Why am I running out of breath at 4-5000rpm

[bsedwebt70-5.0]

Mine was a dirty fuel filter - I had the original tank in the car and ran fuel cleaner in it and it started taking out the old gunk in the tank - it would clog up a fuel filter in a few hundred miles - I kept changing the filter until it did not clog any more - I used clear plastic filters to tell when it needed changing after the first one.

 

[C0V3R]

Got the AEM wideband installed today and went for a run. I'm idling at 11.6:1 and cruising around 12:1

On most WOT runs it starts off around 12:1 and moves up to around 13.6:1 at around 4500-5000 although I did see a 14.x once.

Would being a little lean up top cause it to stop revving?

 

[C0V3R]

Mine was a dirty fuel filter...

Checked my fuel filters (pre pump and pre carb) and both are clean. Good idea though.

 

[D.Hearne]

Got the AEM wideband installed today and went for a run. I'm idling at 11.6:1 and cruising around 12:1

On most WOT runs it starts off around 12:1 and moves up to around 13.6:1 at around 4500-5000 although I did see a 14.x once.

Would being a little lean up top cause it to stop revving?

Well, Yea, it would. An engine's only going to run as fast as the available fuel will permit it to.