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Old 06-28-2020, 06:31 PM   #4
Scooby Newbie
Member#: 187315
Join Date: Aug 2008
Chapter/Region: MWSOC
Location: Chinatown
2007 WRX TR


Thanks for posting this. Iíve been trying to troubleshoot a low power low boost issue on my 2007 WRX TR, car has about 60k miles. I installed a TD05-18G with supporting fuel mods and in my current tune runs 22 PSI tapering off to 18 psi. The tuning was by me using Romraider and I aimed for a safe knock free tune with conservative timing in high load areas with afr of 11:1.

I ran this tune for a while (weeks) after I was happy with the results but then I noticed that max boost was down to 19psi one week and worsened to 12psi eventually.

I havenít done a compression test yet but my boost gauge shows strong vacuum (-20) at idle and it passed the oil cap smoke test.
Generally the car runs and feels strong with the only symptom being slow to build boost.
I also did the wastegate tests you mentioned in the car boosts the same. Much slower and sluggishly than before and only reaching 12 psi max.

Assuming the motor is healthy as is the new turbo (about 2000 miles on it) I suspected possibly a pre turbo exhaust leak or maybe a clogged downpipe, which is when i came across this post.
The downpipe is an aftermarket catted (SRS brand I think) and has about 50K miles on it.

Thanks for the information, Iím going to pull the downpipe off in the next week or so and check it out. Hopefully thatís it ...Iíll try and report back whatever I find.
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