Chevyhead

Hey I'm new here, my 01 Z28 started to act weird. First the check engine light would flash when I got into it but nothing felt wrong it didn't feel like it was misfiring and the check engine light would turn off and run fine. Now if I go over 2500 rpm it will shake really bad until I get out of it and get under 2500 rpm. I'm new to fuel injection and computers so I thought it was maybe a broken valve spring or maybe a bent push rod yet when I looked nothing was wrong.

I put new injectors, spark plugs, and wires in the car and it still does it I even got it tuned and it still does it one thing the guy said was that my o2 sensors weren't sending any info into the ecu and I got new ones and they still didn't work. So I'm not sure what to do. The guy that tuned it said that it might be a bad harness or ecu. Has anyone had this problem? Its really kicking my *** and I want to try to fix it.

The car has a custom grind cam (the guy I bought it from has no idea the specs) and longtube headers