All great suggestions! However, have you fully applied the KISS principle?
I just went through something fairly similar with my 1GM10. Over the winter i replaced my copper fuel lines
with hose purchased online. Unfortunately, this hose was slightly to big enough and i ended up having to get hose at the local marine store. All they had was silghtly too small enough, but I got it to fit enough to get a clamp on it.
Bled everything from tank to injector, hit the button and it started right up BUT wouldn't rev under load any higher than about 2100 rpm. I went through everything again to check for air leaks, still no revs. I replaced the fuel
filters twice, even though the first pair were put in fresh for Spring Commission. I even went so far as to pull the injector and ended up replacing it as the shaft wouldn't slide in the cylinder. No joy on the revs.
Engine and drive train ran fine last year, all i did to muck it up was to replace the fuel lines
. Couldn't (shouldn't) be prop, trans, fuel
injector, lift pump
, filters, rings, pistons, etc. Had to be something I touched. 3 days later, after going over the whole engine multiple times, i bled the flappin thing again, One. Step. At. A. Time.
Runs like a top now. Make no mistake, ANY air in the system will haunt you! I'd suggest bleeding it again thoroghly!