I have an 86 xj 2.8l v6 it has an erratic idle and no power when driving. I have rebuilt the Carb. New egr, fuel pump, new fuel filter, PCB valve, new air filter and still runs like crap. When I hook up a tach and set the timing, the Rpm's are OK but the timing with the light bounces. Goes from 10 -12 bouncing back and forth. When I Rev the engine, the idle lowers but doesn't completely return to 700 rpm. It stays a little high and slowly drops back down. Not sure what else to do. At a loss. Any help would be appreciated.