Even with all the previous modifications, this engine still didn't have good power at high RPMs in the 6000 and up range. No amount of tuning seemed to make much difference up there so I decided the intake manifold runner size was the problem. The intake ports in the head are 1.370" and the EFI intake runners are 1.25. It was interesting to see that the old SU carb manifold is the larger 1.370" size yet the EFI manifold was smaller

I ran across someone selling a custom EFI intake manifold that sunbelt racing engines had made for them and decided to give it a try. The difference was night and day using the exact same size throttle body as before. I had to add 20% more fuel from 4500RPM and up to keep the same mixture and now the car pulls like a ROCKET from 4000-7000. I just thought it was making power at 5000+ before! Obviously after seeing this first hand, the EFI intake is a serious problem for a performance engine and unless you're going to be happy with the stock cam, the EFI manifold HAS to be replaced. Unfortunately there is no good solution other than a custom fabricated unit (expensive) or going to carburetors. That said, a set of dual SU's or triple weber carbs will far outperform EFI unless the EFI intake is replaced.

Below are shots of this new intake manifold installed on my engine


Here are pages on earlier mods done.
Here's a page on installing internal regulated alternator on a early car