Are you saying you timed the pump off #1? There is a mark on your crank pulley marked FE. The crank position should be there when your MFI pulley is on its mark.

I missed this....Can you confirm how he timed the pump? TDC #1 or TDC overlap #1

I will check...

Are you sure you expert is expert? I don't think it's been mentioned but with your symptoms
I'd check the thermostat and hot air hose to it

I had problem with the warm up thermostat and removed it. We had the pump sealed and set to supposedly proper setting.

It ran well cold and when it warmed up it was horribly rich. finally I removed the warm up stack and made a cover with a 6mm bolt that would push in the lever manually. I use this for overall rich lean adjustments. Solved my problem.

I also permanently installed an AFR instrument with MAP, RPM and AFR readings and this allowed me to tune the system.

There are a few posts on this.....I will look for the thread.

Have you checked the fuel rack to see if it is free and snaps back?

Again thanks to all for the advice...I'll address the last three notes here:

Thermostat is spotless and moves freely, hot air hose from heat exchanger is new and secured properly. The thermostat gets hot. I do have old heat exchangers where the hot air jackets are a bit worn...leakage around the headers...but still throw heat.

I gave the car to my mechanic and he drove it around with the exhaust gas analyzer up the exhaust pipe (some times it feels like I'm getting it up the exhaust with this car) and that's where he's picking up the rich mixture at the low and higher rpm range...where mid range it tending toward lean...not so much as to cause an issue with the engine though. He was explicit in that he never adjusted the mixture at the pump by more than two clicks...either way.

The fuel rack is free, and the bushings are tight...no air leakage there. I haven't measured the connecting rod...but I'll assume the mechanic did, so I think the linkage is set up properly.

When I got the car back from him it ran well, not perfectly - as he'd hoped, on the highway it was fantastic...so I know what I'm looking for...but afterwards on the way home through traffic things began to go south and since then it gets worse every time i take it out...now it bucks and backfires...like it's got water in the fuel. One last thing...maybe it's me...but the fuel mileage seems very low...maybe 10 to 12 mpg... I drive a Cayenne GTS for an everyday driver and that thing is in the high teens in city traffic....so it tells me there's a real issue with this 911.

I will check the fuel filter this weekend...hopefully it's clean...got less than 200 miles on it.

...and I thought Boats were tough...

Did the car ever run well in your possession?

If not is it possible that the engine has a different cam than matches the one in the pump?

Wayner...Not really...That's why we're leaning toward sending the unit to Pacific...it seems to be an issue that we can't get fixed...without taking the pump off...and there only a few guys out there that know what to do and how to fix these pumps.

This bothers me a bit. The procedure is quite specific. You must get the part-load adjustment correct before you even bother trying to set the idle. Your comment about him driving around with a sniffer up the tailpipe also sounds like a bit of a seat-o-the-pants approach. Setting part load requires driving at the precise throttle setting/rpm/load. It really is a strange process, but makes sense once you understand how it all works. Makes me wonder what else might be guestimated by "one of the best guys in the NE".

Quick and easy to check the pump rod length (114mm), and the throttle push rods (149.5mm, +/-).

My biggest suspicion would be 200K, not 100K on motor, and lots of wear (shot pistons, worn cams, leaky valves). But you seem to have looked into that already.

10-12 mpg is not normal.

Your description of running OK at first, but getting worse over time, might point to other than MFI. Really is nothing that should change in the MFI, once it is set correctly. Cleaning and gapping plugs should make no difference, unless there is an off chance you switched a plug lead somewhere (that will definitely get you backfires).

Don't give up. There is a reason. Patience and methodical testing will find it.

Also with a 72T in my shop right now, working through the MFI for a friend. Previous owner had "tinkered" with the MFI to the point it was undrivable, and put on a set of carbs. Turns out nothing wrong with the MFI, in spite of being in a box for 15 years.

DG

Post a pic of your fuel filter console area.

After walking away for a while, I returned to the car with a clear mind and started to go through the check list. One by one I hit each until I came to #6 - Fuel Flow and Pressure. I paused and then I came to the idea to look at this from the point of view that I should check the entire fuel system. Earlier I mentioned I have had the electric fuel pump off twice to check pressure and flow, so I knew that was in decent shape.

I started in front with the tank. It was replaced earlier this year, so I decided to check every fitting, fuel line and clamp. I found that the sender on top the the tank was loose, and a few hose clamps were loose as well. Every screw and every clamp was tightened. From there I went on to the fuel filter console, hoses and camps were re-seated and tightened. I also spun off the filter and drained it...It was here that I found a major issue...water in the fuel. My guess is that with all those loose fittings, the ethanol just sucked the moisture out of the summer air and left me with a nice mess.

So a new fuel filter, some E-ZORB(water remover) and a lot a patience driving around to burn 3/4 of a tank of crappy gas...and I began to realize that the car was coming around to it's old self.

This morning I filled the tank, at a different station just to be sure, and drove it on the highway, back roads and in stop and go...It now idles at 750...smooth and steady...acceleration is good...could be a bit better but a huge improvement over what was. It was like it had a virus and it just needed to be cleared...

I think I'll drive it until I need a refill before I do any thing else.

To all who weighed in on this issue and talked me off the ledge, I want to say thank you...The smile is back

I'll keep you posted on my future results.

You might try to find a station with ethanol free gas.

I chose sending it to Gus. When it came back, I carefully reattached it on the block. I had also had my injectors cleaned (locally) and made sure my fuel line was clean. It runs fine, now.