What else can I do for a p0300 code?

You may need to do a compression test both static and running, you may also want to do a leak down test of each cylinder. those motors are known for cam shaft issues which can give you the P0300.

After the work you have done .. *CRANKSHAFT POSITION RELEARN PROCEDURE* must be performed.. Professional grade scanner & 'operator' required! .. Otherwise PO300 shall remain!!