Check the fuel pressure under WOT. My old pump gave fine pressure at idle and under partial throttle but once you put the demand of WOT or high rpms on it, it would pull back and buck. Might be ignition related but sounds like fuel delivery to me.
Edit- Oh wait you have a TPI, those feel like a brick wall at 5K unless you made mods to make her breath up top. I owned two TPI's and both did not like the 4800 + area of the rpms.
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