Any chance your brake booster diaphragm has a leak, leaning out those cylinders by creating a vacuum leak?

Can you remove the booster line and apply vacuum and see if it holds the vacuum?

How about adding wide band O2 ports to the HEs and measure your AFRs (both sides) on a dyno?

Doug

It just speculation on my part, but it may have combined with some intake leakage on the left bank, and did it in.

Usually one set of dyno runs is sufficient for remapping to get it to within 95% of target. If the air fuel ratios are severely off, as is typically the case with Autothority's MAF chip, it may take a second set of runs for final tuning. Here's a thread on the same setup which shows the before, and after results with two tuning iterations. More power was actually achieved with less ignition advance by correcting an overrich condition:

http://forums.pelicanparts.com/porsche-911-technical-forum/259587-looking-fabspeed-catbypass-dyno-results.html

MAF is only worth it if done right, it's just another component like a piston is to an engine, otherwise you are better off with just the stock flow meter and a chip. The quality and power gains of a MAF is all dependent on the software and the person who developed it to make it work, and it needs a special dedicated program. The stock chip, or any aftermarket chip will not work. Fine tuning for your engine gets you at the center of the bell shaped curve, otherwise you'll normally just be in the blue or green region.

http://forums.pelicanparts.com/uploa...1157508549.gif

Some owners are very happy staying with the Autothority MAF and a remap, others went back to the stock flow meter with a chip because they felt the power, refinement, and response was better. I like a MAF system, but only the Bosch HFM5 system you see on my site - with software and technology much superior to the 25 year old Ford hotwire setup. If you decide to stay with the MAF, I recommend contacting Professional Mass Air Systems, as they are the newly reformed company that took over Pro-M when they went out of business. http://www.massairsystems.com/ Pro-M was the company that made the MAF for Autothority. A few years ago, they replaced the K&N filter with a dry media type cone to address the oil contamination issue that was so prevalent.

After 1500KM, I performed a leak-down test, all cylinders are within between 0 and 1%, so I am pretty satisifed that the rings seated, or is that a bad conclusion from a leakdown test?
Haven't really got a sense of oil consumption because of the number of oil changes.
I spent a bit of time on a dyno and got the following A/F info - it looks to me that there is a pretty good chance that the lean condition in mid range caused the detonation that broke the rings.
http://forums.pelicanparts.com/uploa...1163955352.jpg
I am planning on sending the chips to Mr. Wong for reprogramming, and to find out what the advance curve looks like. I think that the lean condition plus likely overly aggressive timing (for the fuel/air temp at one track session) are the root causes of teh broken rings.
However, I am really on the fence about whether to retain the (old) Autothority MAF that has been on the car for more than 10 years, or revert to the stock setup. Any suggestions/opinions?

hi Bob...wondering how this all worked out for you...did you return to the oe/barn door set up...??
could you please summarize all that you did...what not to do...any further insite as to what may of caused the problem...?? did you ever check vacuum on the brake booster...??
Thx for your reply either here or pm...considering a new intake set up for a stk 3.2L engine...Bob

Wow- talk about dipping into the archives !

It worked out well - 20,000 KM and many track days later I still have good leakdown results.
I kept the Autothority MAF, and I arranged with Steve Wong to take the data from the initial dyno run and provide a new chip to correct the A/F ratio, and to reset the timing a bit so 94 octane isn't necessary.
That chip resulted in the following:
http://forums.pelicanparts.com/uploa...1390685784.jpg
This improved the A/F to a degree; the above data was then used to refine the chip.
I have not been back to a dyno since, although I plan to do so this summer.
I am pretty satisfied that the original issue was lean condition/high temp/91 octane fuel, and that the iterative approach to getting the ship right is the correct way to make sure all is OK.
I checked the brake booster and couldn't find any leak, although as I recall it was a fairly crude check.
Not sure if that gives you what you need - pm me if you want to chat further.

thank you...pm sent