throttle body spacer (what does it do)

[jsconiers]

Stupid question....How does a throttle body spacer improve performance?

[chicane67]

Increases plenum volume... and depending on material, it might insulate some temperature.

[Lowend]

I've found in most stock-truck applications they don't do anything.
Some of the newer Jeeps respond well, but that's about it.
If GM could have made real power by adding $.05 of aluminum to the back their throttle body, don't you think they would have.

As for adding one to a custom F/I setup... well that's a different story, but I still wouldn't expect anything staggering

[Adam's 55 Chevy]

They are cheap enough to try and see if there is any improvement. But I feel that a lot of go faster add ons are in the mind of the purchaser. You fit a brand new doo dah and drive harder 'testing it' so you 'feel' it has worked. Yes it may improve performance a little but not that you would notice it as much as some other improvements. Think of it as part of a complete package of performance upgrades and not a stand alone item.