Lt1 lopes and surges....

Put a new Accel opti spark, coil, ignition box. Can ran great, then I tried hooking up an autometer tach, to the coil wire. Now when you start the car it lopes and surges, no vaccum lines are off. I have a accel ignition box on the car, (fuse is good on ignition box ) and so are all the other fuses, And its not throwing a code.... Whats the odds of the ignition module being bad?? Or any suggestions??? I tried putting the stock coil and ignition setup back on the car and it does the same loping and surging...