2004 STI with 68k on it fully factory, I have been hearing a slight buzing sound come from my throttle body when the key is set to Acc. and also when i listen right after i turn the car off. what is it? maybe the plate sticking? any helpful hints would be great. i am running a lil rich out the tail pipe, i am thinking this may have some thing to do with it. also my MPG is not great avg. of 19- 19.7. and that being very light on it. i have heard that from fac. they run a lil rich but can be tuned to run better and more fuel efficent. Is this true? Thanks for any info. ps only use premium gas.