I have a Richard Clark rebuild powermaster installed three years ago with zero problems. The give a lifetime warranty al lomg as they are around. The contact is Pete Hoffman. I also had them rebuild a spare complete powermaster as well. Expensive.
I run e85, 120 inj, hellcat fuel pump, stock fuel lines, ecugn, ecugn controls fuel pump, Colorado coil. 6262 turbo. No problems at all including fuel pressure.
" I decided to replace with Comp Cam 980-12 which I hear are a good stock replacement." This was a mistake. These springs wear out quickly just like the original Buick springs, The correct springs for a stock motor are Comp Cams 981-16. This way you eliminate floating valves on a stocl motor.
Sometimes you just have to start over. Take a day or two off and slowly follow the no start tree verifying every part on your car. Something is screwed up and is most likely a bad part you thought was good or a screwed up engine wiring harness.