I've been chasing this power issue for a while.

Here's the symptoms. In first and second gear, there is no problem...the car pulls hard and quick right up to 7000 RPM. In third gear it starts to faulter around 6000 rpm, and in fourth gear it is a dog anywhere above 5000 rpm.

This screams "not enough fuel". Here's what I've checked.
Fuel filter: it was fine, but I replaced it anyway.
In tank pump: working fine.
In line pump: Pegs my 100 psi fuel gauge when not running and holds at 95 psi while car is running.

I'm almost convinced that the problem lies within the fuel dizzy assembly. Should I mess around checking or testing, or just replace it all? Is there a rebuild or cleaning procedure for it?
Thanks in advance for your help, Mark