You could pull the O2 sensor and attach a vacuum/fuel pressure gauge to see if there is excessive back pressure. Not sure what a good number is but anything over 2 PSI is probably not good. The factory manual mentions excessive back pressure four times but does not tell what good is.

 

So I finally checked the fuel pressure today. While running it held a constant 30psi which is perfect right? Also checked the regulator, pulled the vacuum line it was dry as a bone, didnt smell of fuel, same for the regulator nipple. While unplugged I checked the gauge reading again, shot up to constant 40 thats also normal right? Then I shut the truck off, went inside for about 5-10 minutes and the gauge did not move so the fuel system seems to be operating normally.

The only question I have is when I first hooked up the gauge I turned the key on to let the pump run and the gauge was at 0? But I also relieved the pressure before hooking it up by popping up the inertia switch and cranking the truck for a few seconds so maybe its ok? When I fired the truck up the gauge was pretty slow to get up to 30 but once it got there it held steady and did not move. Does this all sound normal to you guys?

 

Sure, that's normal pressures for low load conditions, but you need to drive the truck or hold the throttle until it hits your problem Rev limiter and watch the fuel pressure. Weak pumps can sustain idle and low load pressure no problem, but you need to check it under load to make sure it doesn't drop as a result of increased load.

 

Well I did rev the engine in neutral, pressure didn’t move. Also let it get to the limiter and still no change.

 

I know this is an old post but did you ever find out what was wrong? I'm having a similar issue with my 91 F-350, 460 / ZF5. It is taking way too long to get to highway speed, won't seem to get over 2800 RPM 3000 if I'm going downhill, seems to be lacking in the power department. The RPM's don't drop, stays pretty steady. New plugs, new wires, new cap, new rotor and no cat...

 

On this truck it was the distributor.

 

My first thought was a defective TFI module, or power getting to one of the pins when it should not. Can't remember the Pin number, but it's a timing-retard function while the engine is cranking with the starter. And maybe there's a rev-limiter built in for when the engine is very cold? Not sure about that, but it would make sense.
Never seen an event like that cause the rpm to actually drop off below 3000 like yours did, but they can easily cause it to not rev above 3000 because that's it's function.

I wondered about the 30psi reading too, but apparently others with more knowledge of this thought that was normal. I thought it was supposed to be more like 38-40 when under load (or with the vacuum line disconnected) and 32-35 at idle. But sounds like I'm wrong on that.
But it sounds like you got it running right again, so congrats on that!

Paul