Since you say it always runs smooth it sounds like there isn't enough
air flowing through the engine.
Look at the air cleaner element to make sure it hasn't collapsed.
Then remove the section of flex hose from the air cleaner to the
passenger side snorkel and see if driving with that hose off helps the
problem.
Is the throttle cable opening the throttle all the way?
Does the cat rattle?

Mark

John Rodgers wrote:
> Have a mysterious power loss on my new engine overhaul. It has run fine
> until two days ago. Now it won't pull your hat off your head.
>
> Engine runs fine. Starts easy, idle smoothly, runs smoothly at any rpm it
> is capable of turning. There is no spitting, missing or backfire. Just
> doesn't develop power to accelerate. Going up hill it just gets slower and
> slower and slower, the rpm will drop to about 1500. Top speef is about 55
> mph. I han't checked the timing yet, but thats next.
>
> Suggestions???
>
> John
>