Hello all I'm new to all this forum stuff, And I'm in DESPRATE need of help.I have a 99 Tahoe and a 91 Chevy shortwide, It has power pulleys, power tower, a super chip, and dumped flowmasters.and i'm having trouble with it. It just started to cut out at shift points or higher rpms, the tach would jump from 1 to 2500 rpm and higher. I had the iginition module tested 4 times and it has come back good, I replaced the pickup coil,new cap and now it's running much worse than before (horrible) The timming is dead on and when the timming wire is unplugged it runs perfect but when I plug it back in and restart the truck it goes to crap, popping, backfiring and almost sounds like the motor is under a strain to run, I am usining a Snapon timming light and it shows the rpms jumping from 880 to 3900 all in between. I have even put the factory chip back in and it makes no difference! Can anyone please help me??? Thanks for any help you can give me.