Whats going on

Question

I replaced both upstream 02sensors,plugs,wires,distributor cap n rotor,fuel pump,fuel filter and both cats and I'm still coming up with a p300 code#HELP

Answer 1

The best way to find this is to do a running compression , anything below 60 psi would be the suspected cylinder or better a leak down test , not a compression test.

​ What also set a P0300 is a crack between the exhaust valve and the intake m this is where a leak down test finds the problem rather than a compression test