Originally Posted by Gumby22

Since replacing the injectors and plugs, have you gotten any codes except for P0307?

Did you check compression on any other cylinders? 150 isn’t necessarily bad, but if other cylinders are pushing 165 or more, then compression on #7 is low relative to the other cylinders and a mechanical problem should be pursued. You should at least check 5, 6, and 8 as a reference. Check #7 again at the same time - compression testing needs to be done when all the cylinders are at the same temp.

Are you certain the rocker arms are moving through a complete stroke? The cam lobe(s) can be partially rounded off and still be opening and closing the valves, but not enough to provide adequate air flow for proper combustion. Use a dial indicator to verify the #7 rockers move as far as another cylinder that isn’t misfiring.

Nobody is questioning that this is a misfire - we’re trying to help the OP narrow down the cause.

There are multiple causes of misfires ranging from electronic to mechanical - ignition timing can be dead on but if there’s a reason the cylinder can’t seal properly, or if a fuel injector is stuck open, a misfire is still going to occur.

Originally Posted by zigblazer

I've read about a lot of lifter problems on the afm engines. Which only show up when running, and sometimes only when warm. Good way to check is start it with the valve cover off and watch the rockers movement. Mine ended up being a failed afm solenoid in the valley cover, but once I got the engine apart, I decided to just rebuild it anyway and delete the afm/dod. My problem was only visable with the engine running because the oil pressure was stopping the valves from opening, cam and lifters were still fine.