Power loss.

[T66]

Originally Posted by Moppie

Well your custom exhaust and inlet manifolds would be a good place to start, then look at how the ECM is tuned, is the fuel pump big enough etc etc.

With a better idea of what its in, how its installed and what your level of knowledge is there isn't a lot we can do to help with out just making educated guess'es.

I understand. Thank you.

[superchuckles]

and you never did say if it was a stick or an auto! automatics lose a lot of power due to the large amount of rotating mass, clutch slippage, torque converter slippage, fact that you're always running yet another hydraulic pump, etc etc..... 42% is still a lot though...... how good are your tires hooking up on this dyno? try another gear - gear position shouldn't matter (theoretically anyhow) -- maybe you have a bad gear or gear shaft bearing & switching gears will put the load on a good one - this is a good oppertunity to see if that is the cause, & then you'll know the cure too.