identifying pcm tune?

[jakebronson]

I just bought a 1999 Tahoe 5.7 Vortec and it appears to have a few performance mods...throttle body spacer, Gibson cat-back, k&n intake system, and judging by the harshness of the shifts I believe it may have a shift kit. My question is...is there any way to tell if the pcm has been tuned? Do the people who tune mark the unit in any way? I would hate to pay all that money for a tune when my Tahoe may already have a pcm tune. Any help would be appreciated. Thanks for your time.

 

[SunlitComet]

dump the tb spacer. there is checking for the checksums in the software but most would not see that. there is a possibility that a tech2 tool might be able to spot it. not always "marked" either. you would need to compare some programming values to another pcm of the exact same vehicle setup.

 

[jakebronson]

Thanks Sun. What are the advantages/disadvantages of a tb spacer?

 

[SunlitComet]

the tb "spacer" on a tbi engine acts like a heat insulator between the throttle body and intake manifold for one and is typically machined to help atomize the fuel better before entering the combustion chambers to help get a a better burn. On the vortec engines like yours the fuel injection happens in the head so unless you can find or build a spacer to go between the intake manifold and heads with with the ability to atomize the fuel more then the injectors can don't waste your money.

On the right applications they can help turn the liquid fuel into a better gaseous state for a more complete burn. On the down side with other modes you might have it may create clearance issues with parts around it.