Random rpm signal, on test bench

[fr.mc.feely]

Using a test bench in college to test my megajolt. the testbench is a fully functioning
93 escort 1.4 also with eec-iv. have not really stripped the whole board, but have cut the original wiring
to pip and saw connections on the edis, and the tps, mj reads the tps signal ok but displays odd rpm signals
jumps from 0 rpm to 2500ish and back down and then may jump to 3 or 4k, while the test bench
rpm remains constant, i have earthed the tps shield to the "body earth" of the test bench and wrapped wire continously around the pip and saw wires and earthed these to the croc clip on the - of the battery.
it still runs up and down through the load bins and jumps up to the proper rpm bins for the brief time that it thinks that its at that rpm for. Is my problem bad shielding. we have a different ford "edis" test bench that has no injection system on it, but the "edis" module doesnt say edis 4 on it, it says ESC and its red, will MJ work with this set-up??????
thanks in advance,
brilliant product