I have a 1999 lexus gs300 automatic with about 230,000 miles, after getting the car I drive it about 80miles and a check engine light came on. I plugged my little scan tool that only tells me the code nothing else, and it said P0446. I looked online and it said the obvious gas cap and/or vacuum leak. Looked also online and seen others with that code and other codes for misfires but they said after they changed the purge valve, all problems went away and the car started to work normal. So could that code be to that pruge valve? Also just tonight had the check engine light flash at me and the car felt like it was misfiring. Checked again and now another code P0305. So with that vacuum leak and now cylinder 5 misfire could it be the pruge valve? And it is leaking oil somewhere, haven't had the time too look into it more since I replaced the vvti o-ring on the timing gear. Thank you