In my '90 744 tic, the car struggled while making boost under anything more than 1/2 throttle. It would bog down a bit and hesitate while making boost, but would NOT do this when under light acceleration.
I was replacing the turbo this past weekend anyways with a rebuilt and RWD clocked 15G turbo from an 850R, so I figured that would fix the problem.
The car now makes boost but backfires in the intake and struggles/feels like fuel cut around 10 psi.
Any ideas?

Running that much boost can be tough on hoses. Bogging on boost could be a bad hose (perforated) and they can be hard to find.

I run my compressor regulator down to 15-20 lbs and pressurized the hose that comes off of the turbo using an altered brake reservoir cap. The escaping air makes it easy to find those pesky leaks.

Randy

Check the plug gap and drain the intercooler along w/ all the other stuff mentioned.

Check your intake hoses thoroughly. Sounds like you might be able to do a pressurized smoke test for leaks.
I think the overboost is mostly on 760's and I thought it came in closer to 90, but I may very well be wrong.

good luck, try not to eat too many red blocks,
Will
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1990 740 Turbo, on its way to stock specs, maybe beyond

Overboost protection kicking in?
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doesn't sound plausible? I have run this car up to 18-20 psi before on a 13c turbo with no such problem until these problems developed months later. I don't think a 744 (1990) even has overboost protection, those are bells and whistles found in the 850, eh?

If you have had it up to 18-20 then probably something else. I do know mid to late 80s do have overboost protection. Backfire? Timing, bad plugs, wires. Maybe check all hoses for holes, cracks, collapsing intake. Just some thoughts.
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this vehicle is also running bigger injectors, 012 AMM, and an adjustable FPR. It is running 4 bar fuel pressure at the moment, and it runs lean at idle. Maybe the feeling of fuel cutout or struggle in higher boost range is a result of low fuel pressure? I was thinking I could up the pressure to 5.5 bar, which is what most BMW turbocharged 6 cylinder engines run.

Think you need to run this over to the turbobricks.com guys. They run that type of psi.
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I finally finished my turbo swap to the 15G but the car still doesn't run right, it idles a little bit rough as if it was misfiring, but not all the time. Also, when I am doing just normal acceleration, the car runs fine..but when I give it the beans, (3/4 or more throttle) the car starts to struggle/misfire again and struggles making boost. While pulling my spark plug wires off, I noticed that the plug wire itself on cylinders 1 and 2 pulled right out of their boots. These are Kingsborne wires (they make ipd's wires) and are less than a year old. I just put the wires back into the boots and the car ran, but do you think that is the problem?
Also, my rear cam seal is leaking and do you think that could be causing oil on my distributor rotor and causing an ignition problem during boost condition?

Definitely suspect the wires. If you pull your cap, might find oil. But that is more likely from distro oring.
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I will replace the wires, cap, and rotor very soon..but what else does this sound like? No vacuum leaks, all hoses look good. The only hose I was concerned about was the hotside IC tube which was quite soft, but I put zipties on it to see if they would break after I drove it and boosted, but they did not, so the hose must be good. These problems still occur even without the boost turned up..if I turn my electronic boost controller off and run the stock setting (7 psi) I have the same issues. I am really getting frustrated with this car and would hate to give in and take it to a dealer.

I know nothing about electronic boost controllers, but the plug wires. Leads me to believe that the spark was jumping, so not running on all cylinders. Had a oldsmobile with a cracked spark plug. Car would miss/bog down only when jumping on it going up hills passing gear. Took a while to find it. And this was a V6. I can imagine 2 missing on a 4cylinder.
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I checked all the plugs and they look fine, I even regapped them to the proper spec and no change.

Guess you confused me when you said "wire pulled out of the boot".
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