Misfiring on boost

[flatboosted]

Problem, My 930 has been extrmely reliable for the past 8 yrs, no problems,. Maintenance incuded new fuel lines from the front pump, etc, always tuned , always ran perfectly
It has the usual mods, Powerhaus IC, K27-7200, Permatune, SC acms, Brian's Rarely8 dual pipe muffler.
My problem occured a few week ago, usual evening drive, stomped on it in low gear, and as it accelerated and went on boost, about 5000 it misfired, shifted to 2nd and it misfired again with a fairly noticable loss of power,
My initial thought was dirty fuel as it was a bit low on gas and I thought maybe i pulled some crap from the tank, . Next morning took the car to a very good wrench in the area, he did the usual check, said fuel pressures were good, WUR operated fine, Plug wires checked ok, changed 3 spark plug connectors, O scope showed the Permatune and coil looked good, cleaned the plugs checked fuel injectors and a couple were dripping so I had him replace all of them.
The car idles perfectly, A/F ratios are correct, electrical is good to the new spark plugs, performance is fine, no unusual sounds from the exhaust. When idling out of gear, you can punch it , sounds great , no popping, etc
When I accelerate slowly or normal everything is fine, smooth, accelerate up to 5500 RPM without punching it everything is fine,
When I punch it it misfires and breaks down just after going on boost

The IC o-rings look dirty and old, not cracked ,just kind of smashed so i have some new ones on the way, I don't think they are the problem though
Since this problem started suddenly i suspect something like the rear fuel pump might be the problem,
Although my wrench said the pressure tested good, I'm curious whether or not the rear pump, if out, would affect the results of a pressure check
Will these cars run with the rear pump out?
Any thoughts?

[quattrorunner]

Check the rotor? I had some symptoms you could compare here.
Boost leak?

[totle]

Sounds like the over-boost switch.
For troubleshooting it can be grounded. If fine then, replace switch.
But do not drive without the over-boost switch on a permanent basis.
It is located on the BOV under the intercooler

Do a search and you will find similar threads

[flatboosted]

The rotor is fine, I'm pretty sure its in the fuel system (rear pump, maybe?) due to the symptoms. I'll check the overboost switch havn't done that yet
Thanks

[Tippy]

I'd try replacing with a known good coil and start from there. Not sure if scoping would reveal a weak coil.

[mark houghton]

Originally Posted by flatboosted

stomped on it in low gear, and as it accelerated and went on boost, about 5000 it misfired, shifted to 2nd and it misfired again with a fairly noticable loss of power,

The IC o-rings look dirty and old, not cracked ,

Pretty classic symptoms of a dislodged o-ring. Depending on how bad the lead, it will run fine until the turbo crams air into the system, and said air has a place to escape...causing a big rich condition on boost. Dirty, old, smashed (should be round, not flat or smashed) o-rings...even though still intact, may not be seating properly to handle the boost. Cheap fix, do that before opening up your bank account for other stuff.

[flatboosted]

Mark, you read my mind, Ordered some o-rings from our host the other day, Mine are intact, just look smashed and definitely not round anymore. The IC has been on and off a bunch of times lately for various work, alternator , etc sure could be blowing off boost. Tailpipes are black and sooty, plugs looked fouled. BIG bucks just spent, injectors were leaky , not shutting off completely replaced all 6 , replaced plugs with NGK BR8EIX, shade hotter than the Bosch W3PDO that were in there. I'll have the new alternator in this weekend and check out a bunch of the items you guys mentioned.
I have heard a strange whining sound coming from the rear drivers side especially when cold, funny sounding , like a spinning shaft with a washer dangling on it , coming from under the car right where the rear pump is. My symptoms could indicate a faulty or failing rear pump. The car will run fine and does, runniing it slowly up to 6000 with no probs. only when you nail it she hesitates like missing, or "Running out of Fuel".
Thanks
I'll update as soon as I get it sorted