Im having boost problems, I used to run real consistent 23 lbs... It was tuned for 93 octane and ran 330 hp and 330 torque on the dyno. I bought the car with mods completed about 4000 miles ago. The 02 outlet came very loose to the point that I lost a bolt and the gasket was damaged. I had a local shop replace the gasket and bolts with factory supplied parts. When I got the car back the boost is irregular. On WOT 5th gear the boost will go to 21 or 22 lbs the engine studders or shudders and keeps studdering while on the throttle. The boost gauge needle shakes and the boost will decrease back to 18ish.. It still accelerates fairly hard but it has a noticeable decrease in power compared to when it was running good. If I roll on the gas in 3rd gear Ill get maybe 20 or 21 psi right away and the boost will decrease to 17ish with a related decrease in power. Im not seeing the solid 23 lbs I used to. In lower gears Ill get a quick 20ish lbs than settles down 3 or 4 lbs. I have Megan Racing 02 outlet, buschur 3” w/no cat., boost controller, K&N, dynoed and reflashed, Any suggestions.

 

Try changing your spark plugs and or getting a boost leak test done.