I have a monster tach in my 91 integra because the stock tach only reads to 8g. My Gsr rev limiter is set at 8600. So when I rev out. The monster sometimes reads 9g or a lil before it maybe after it. Why does it flex around... Is there any way I can get a 100% or as close to reading?

 

actually the monster is closer then stock. THe stock can read 500rpm off at higher rpm.

I dont think there is a 100% rev counter, maybe something like SAFC that is electric, but even then i am not sure if that is 100%

 

well Vtec is set to 5200 and when it engaes the stock tach reads 5200 and the monster tach is like 5500

 

In my experience with tachs, the stock is never accurate. My monster tach was the more accurate of the two...It also depends how you have your tach hooked up. I had mine hooked up at the distributor, can't get much more accurate than that.
I don't have vtec, but it sounds like your vtec is engaging late....but I dunno.

Vic