ok... so i did an oil change and coolant flush the other day and reinstalled a new oil feed line for my turbo. but now, my tach is all messed..... it looks like its gettin the wrong voltage or something because when im driving it dips down and back up and back down and sometimes droppin to zero and stayin there. sometimes its accurate though....like at idle, or when i redline a gear or something its right on. it changes when im crusin though. wtf... no CEL and the tech is not doing what my engine is, i can hear it and feel it. so its gotta be just my tach but i cant figure it out!!! any of you ever heard of this before? i reset my ecu and it still does it. actually, i reset my ecu when i was doing my oil change and stuff and thats what made it do it in the first place, so i really dont know

any help MUCH appreciated, tia

What did you tap for a tach signal? It may be a bad signal, or you bumped a wire loose somewhere.