I just recently purchased a GMS Throttle Body for my car and after installing it, my car first sounded like I had switched out for new cams, then when I accelerated while the car was on park, it would rev to like 3000 to 4000 RPM, but it would take like 9 to 10 seconds to come back down to idle. It also threw a check engine light as well as the dreaded wrench. I turned the car off, then put my original back on, and no problems whatsoever. I have attached a pic of the TB below, any comments that may be of help are greatly appreciated.

 

What was the purpose of the new TB? Your sig doesn't show that your aspirated and the stock TB is tough to beat for being NA. I suspect the new TB requires revised tunes.

 

Just passing along some anecdotal evidence... but pretty much every TB swap ends the same way. Rough Idle, surging, hanging revs, just plain not running... Keep your stock Throttle body unless you get forced induction. Then get the GT500 body.

 

get rid of it. its not going to give you any real gains and they are known to cause problems just as you have stated above.