Starts hard AND runs like crap? You need to:
1) Pull valve cover and verify timing chain stretch (should be zero to 4 degrees). Timing chain inspection procedure is at
this PDF file.
2) Check IP timing (start of delivery)
My money is on #2. Especially if you had removed, then re-installed, the injection pump. Wouldn't hurt to crack one injector line at a time at idle, see if any 1 particular cylinder is causing the problem.
