Originally Posted by jcat_GS3

check the fuel filter. If you've cleaned injectors, replaced plugs, had an oil change recently, my money is on the fuel filter. If you're getting a CEL get the codes pulled at autozone and post them here. this should tell us better where to look. That mechanic of yours seems like a real piece of trash. Take the car elsewhere.

So you can see where i'm getting this from, your hierarchy of missing/shaking/pinging problems:

-air filter
-spark plugs
-fuel filter
-clean maf
-clean throttle body
-fuel injectors
-fuel pump
-vacuum leak
-head gasket

Originally Posted by GS4_Fiend

IIRC, the fuel filters on the GS is in the fuel tank. Not changeable.

Originally Posted by jcat_GS3

however, with a car that has over 100k miles the fuel filter can very easily need changing, especially if the car was not run with premium gas for it's whole life.