P0300 is random misfire. There are a lot of things that can cause that on a VG33E engine. You wan't to make sure your sparks plugs, ignition wires, distributor cap and rotor are all in good condition; it is important to read the old spark plugs for abnormalities, such as carbon fouling or blistering. Make sure there are no vacuum leaks or splits in the intake duct. Confirm proper fuel pressure and perform a fuel pressure leakdown test using a fuel pressure gauge. Check engine compression. Check ignition timing using a timing light. There are many cases where a bad distributor can cause this, but you need to start with the basics.
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