Where did the power go???

[selser420]

I've been driving my car for the last few weeks with the boost set at 14-15psi. The logs have looked good and the car has been running great. I parked it in the garage on friday and didn't touch it all weekend. My boost gauge isn't 0'n out when the car is off and I was told that I should add 1-2psi to my actual reading based on how far it is off(thanks oldman!!). When I took it out on Sunday night, I turned the boost down a little bit to account for this. Other than that, I didn't touch a thing(yes I turned it the right way!!) After letting the car get up to temp, I get on it and it falls on its face at full boost(12-13psi actual).
The next day I did a boost leak test and changed the plugs. The plugs didn't look that bad, and they only had 3k on them. I have a small leak that appears to be coming from the J-pipe/turbo outlet connection, but this leak was there two months ago when I did my last test. I also hear air coming from somewhere on the back of the motor, either the intake gasket or the valve cover gasket, but I havn't pinned it down yet. This only makes noise once it gets to 18-20psi. The new plugs seemed to solve the stuttering at full boost, but it has still stuttered randomly a few times and the car doesn't feel like its "all there"( not as smooth spooling up) I haven't got a new log since, but will try tommorrow if the sky ain't pissin'.
I don't get why it went to shit after sitting a few days!! Could messing the MBC have caused this??? I wouldn't think so but...... Do MBCs ever need any maintnence or internal cleaning? Any other suggestions?? I just don't get it, the car has been running great and pulled awesome when I drove it on Friday.
Thanks for any input and suggestions.....everyone here has made owning my first DSM much easier...and yes I'm hooked!!

 

[oldman]

A boost leak is a boost leak and you should fix it no matter how small it is though I agree with you that it should not be the cause as you're able to pressurize to 18psi.

I get on it and it falls on its face at full boost(12-13psi actual).

Please explain.

Any other work done? Problem just started after you adjusted the MBC? Any other problems? Reason for you to question the accuracy of the boost gauge in your other thread?