Classic "TPS Out Of Adjustment" symptoms:

http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

Why do I think that? Because without the timing jumper installed the base timing is, you guessed it, 12 degrees BTDC. So if the TPS IDLe adjustment is out of whack, then the timing jumper does nothing, so you end up with 12 BTDC timing.