Next step in troubleshooting miss fire issue.

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Car car was running horrible and had a massive PCV leak putting tons of oil into the intake only code was a MAF sensor code, replaced the MAF, replaced the PCV, removed and flushed all the intake pipes reinstalled and test ran, still ran like garbage and getting misfire and fuel system codes so I put in new plugs and coils (also did a compression test at that time 175-175-180-180 cold engine) and re tested still getting fuel system codes as well as hard cut when driving but no miss fire codes. I then replaced both fuel pressure sensors and still got codes and hard cut and while reading up on possible problems I was reminded that the intakes can gunk up on GDI so pulled the intake and did a walnut blast and had the injectors cleaned and tested, I reinstalled and and still getting fuel codes Wrote them down this time P0089 & P2293, replaced the HPFP and fuel system codes are gone but now getting P0300-0304 codes. Car is stock other than an tube style intake and 3" turbo back exhaust.

How long has your 2007 Volkswagen GTI had this problem?

<300mi