I just bought a 03 WRX (not an STI) just wondering a few things. I believe it is stock as of now, what is the best sounding muffler for it. Also is it ok to run the K&N filter in it. I heard some things about some turbo cars dont do well with the oil in the K&N filters, it meeses up the mass air flow. One last one what type of oil should I run in it, Synthetic? Thanks for any info and help.