If it's EFI, the only thing a spacer will do is lengthen the runners, giving you more low end torque (overall). Not exactly the thing for more top end, so you may be better off with another intake for best results. Was the dyno operator not impressed with the low end of the car or what? Scan & post some torque curves for us, please....and also a list of modifications. I'm shooting in the dark without more info.
If it's a carbureted application, I really don't know.
