Leon 1.8t FR -05 engine problems..

Mar 15, 2023
4
2
Hello everyone. I have owned this car for a month, from the beginning there has been a problem with the variation of boost pressure, When accelerating in 5th and 6th gear with 3/4 gas, the boost pressure pumps from 1bar to 1.4bar based on the boost pressure gauge reading. That is not a big problem, but when driving at half throttle in a lower gear, the drive is stuttering. I have changed the plugs, fuel filter, air filter, pcv valve. The MAF is quite new Bosch (tryed another MAF too, no change) I have checked vacuum pipes and changed one faulty pipe. Car has 3" downpipe and decat exhaust systems with one Ta-Technics muffler, previously the car had stage 1 programming, but now a modified custom program. The engine also makes a screeching sound at half-throttle, as if the exhaust manifold is cracked, and a whine is also heard before the boost pressure rises, I've tried to pressurize the supercharger pipeline, but I couldn't find a leak. I also removed the turbo and checked but could not find anything wrong.
The car has a Forge bypass with a stiff spring, the original bypass has been ordered, will arrive next week. Error codes never appear, lambda values are fine, all values follow requests, tested with a test drive with the creator of the program, still, the maximum amount of air remains insufficient (169g/s) and the car feels a little inefficient.
The car idles nicely and the emissions were good with the catalytic converter in place. The only note is that the temperature of the coolant is only 80 celsius when checked with vcds,
Is there something wrong with the cylinder head or where are these symptoms coming from?
Sorry if my writing is unclear, made with google translator..
 
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