General Maintenance & Repairs - Rough idling in drive

whats up guys i have a 98 z28 A4 and notice that when the car is in gear it idles rough almost like its missing but the tach is holding steady and there is a distant sound that if i had to put into text would be a rump rump rump...rump rump rump... that can only be heard in the car, when i stick my head out of the window i cant hear anything, also if i idle it up in drive back to a grand it runs smooth and no sound, i just changed the plugs (.05 gap tr55) and msd wires... just wanted to see if anybody has any ideas or has had this problem

Check plugs and wires again. A wire could be arcing if its too close to your header. ALso check and make sure all the coil packs are connected on the rail. I accidently pulled a wire apart while moving them around on a tune up.

everything is how it should be and no arcing..thinking maybe i need to pull the plugs again and lower the gap to .044 to fix the idling issue

NO.....you can't have a better gap than .050

I was going to say, if none of the wires are touching and of the metal exhaust manifold piping......you may have cracked a plug while putting it in. Or maybe a bad new wire or one thats not snapped on all the way.

.