RPM tach going crazy

[WannaBeGearHead]

I am asking this for my buddy who has a 05' V8. He said he was having problems with his rpm tachometer ever since we changed his headers. After that he said the rpms would be off almost all the time. Sometime they would be off by a few hundred RPMs (sitting at idle would read 0rpm) and sometimes would read 3k rpm while sitting at idle. What do you guys think it could be? He said he doesn't feel any power difference, he just thinks it is the tach that is off but doesn't know why that would or could be.

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[PHX8839]

I would say run it on the tune that he had before and see if it's still off. If it isn't something in the tune is wrong and f-ing it up. If its still screwed up the gauge cluster is bad. That sucks too cause if you take it to the dealership (the only way to get the miles to be programed cortrectly) your car will be down a few days and your out about $600-$700. If you get a new cluster somewhere else and install its yourself the mileage will be off. As far as I know only the dealerships can get them reprogramed. Also, you will have to re-load your stock tune when you bring it to the dealership. make sure tehy don't change the tune at all or your new tune will not work.

[WannaBeGearHead]

He doesn't have a tuner and he installed shorties so the tune isn't the problem. The rpm gauge goes crazy. He wants to know if it is a cable that runs the rpms or a sensor gauge that is bad.

[WannaBeGearHead]

Really? No one? Would like to get an idea of what it could be.