my buddy has a 98 gst. its all stock with 70,000 miles. when he lets the motor rev up to and over 4500 smoke comes out of the exhaust. i was thinking 1 of 3 things. bad headgasket, bad valve seals, or bad piston rings. my plan is to do a compression test then pull the heads off and check the head gasket, check the back side of the valves for oil buldup or residue, and check the cylinders for scratches. if there is oil on the back of the valve and not just on hte face then the seals are bad, if there is scratches on the cylinder walls then its bad rings, by looking at the head gasket will tell me if it needs replacing. any of you guys have any other suggestions or tips.this is just what i came up with i know if there is something im missing you guys can help.thanks.

 

are there signs of coolant in the oil or vise verse? what color is the smoke? how bad is the smoke? another thing could be exhaust seals in the turbo are going out. check for oil leaks and boost leaks. it could be just something stupid. it doesnt necessarily mean its anything that significant. just check all the easy possibilities like boost leaks, oil leaks, turbo shaft play, compression, etc. dont go ripping the head off if there is absolutely no reason to pull it off.

 

+1

 

the smoke is light white. after accelerating when he lets off the gas a puff of smoke comes out. ill check the simple stuff first well do it this weekend and see what we find. thanks.

 

Check the pcv valve. Might be clogged. Put a new one in and see if that helps. Start with the little things first.

That was my problem when smoke came out of my exhaust. It kind of sounds like you had the same prob as me. I thought it was my valve stem seals.. but it was just a bad pcv valve, and my catch can.