I have a 93 Z28 M6 with 101K miles on it. I've recently been going to the drag strip and really taking it to high rpm's through the gears. FYI, the tach has yellow hatch marks before the redline where in the middle of those marks I shift. I just noticed this problem because like I said, I've only recently started taking it up to high rpm's in the gears (2nd, 3rd, and 4th). Well the problem is that when I get at or near the hatch marks, the car starts to feel weird, it slows then goes, like a speed governor would do only it does it very fast, like one right after the other (ie: back and forth, back and forth). It's not terrible, just noticeable. I'm wondering is this signs of an ignition problem. Any info would be greatly appreciated.

 

Kinda sounds like the rev limiter to me, but you can't be hitting that in the yellow. Could be fuel related (as in not enough). It could be a knock condition too. I know that sometimes shows up on a dyno graph as peaks and valleys in power.

 

The tach is not that accurate. It's entirely possible you're just hitting the rev limiter without the tach going in the red.. Try some logging next time to see what's going on.

 

I know it's not the rev limiter, could be the fuel filter, hasn't been changed for 50K miles. I'll have it changed and see if it makes a difference. Thanx guys.