sounds to me that we have the same issue... except mine is with my 1-year old mopar fuel injection kit on an '87 4.2.

in my case, under heavy acceleration, there seems to be a "chatter" noise @2100+ rpms. worked on the timing and i still have the noise. i know it has to be from the engine/mopar kit because it wasn't there prior to the kit installation.

i'm still trying to narrow this noise down.

4.2 '87 yj, 263,000 miles, mopar mpi, 33" mud bfg, skyjacker 4", 3.73 gears, arb lockers-f and r., tom wood's 2.07 shaft conversion, tom wood's hd driveshaft, magnaflow/custom exhaust, 4wd bumper/swing-out tire carrier