Ive heard something before about our tach not being accurate? Is there anyway to verify your tach?

 

Hook up a "scanner" and read the PCM. It will give you the correct RPM.

 

some other options:

go dyno your car and check versus the dyno output.
Get a shiftlight and compare.
Your idle should be easy, then just check the high end by running it to the rev limiter.

Ok, so the scanner is probably a better option but i you don't have one then there are some other choices. I've found mine to be dead on accurate using the above 3 methods (i didn't go on a quest one afternoon, they were different times).

Not everyones tach is off like some people make it sound. I've had people ask me where i shift and then for some reason try to factually tell me that " you do know that your tach is off."

-brent