i have a 98 gst. i did a boost leak test and i heard a hissing sound up near the throttle body. what things could be leaking up there besides throttle body?. or would it jsut be that. i know its not the ic elbow pipe becasue that has a brand new gasket. im thinking between TB and Intake mani.

 

Yup, TB, vacuum lines, BISS, TPS (plus its gasket), cable pulley (plus its gasket), MDS...um sensor, fuel injectors...yup, FIAV, IAC, fuel injectors, intake mani to head (doubt it though), that's pretty much it.

 

i would also check the TB shaft seal. These are known to leak and cause boost issues. Check to if the air is comming from the area near the throttle position sensor. If so then check out this write-up
https://mitsubishiforum.com/m_104128/tm.htm

also note the last post tells you where you can purchase the seals from

 

engineer i think thats exactly where it is leaking from. when i heard the leak i pushed on the throttle cable on the side of the tb to like shut if more and the hissing sound went down a good bit, and when i let off it went up again. sound like Tb shaft seal?

 

replace them anyway. they are cheap and easy to do.

 

yup, id just replace them and see if it solves the problem