Real world throttle body experience?
 

Just wondering if I should believe American Muscle when they say their replacement will add 20hp with no change needed to my tune. For $350 I'd do that if true.

Depends.........& don't know what you're driving.
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My 2011 was tuned for a twin 65mm T/B, flows 1517cfm.
Upgraded to a mono-blade, 65mm x 147mm, flows 1797cfm. There were no adjustments made to the drive by wire tables in the tune, picked up 20+ whp. Took a few driving cycles for the ECM to figure it out.
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I have a 2006 with stock twin 55 mm and a tune from a local performance shop. Looking at either a SR performance or BBK with twin 62 mm ports. I've read elsewhere to expect better throttle response but not much HP. The tune really took car of throttle response, so I wouldn't look for any improvements there.

What does your throttle body question have to do with:
You need to post in the correct section -

Fair enough. How do I move it?

I asked someone with mod powers in this section to move it

Leave the throttle body alone.

Thanks. That's kind of the way I was leaning.

I replaced mine with a GT500 TB that i got for $225 i think. Didnt notice anything substantial in gains. I have many other mods to free up airflow too so hard to believe that its really worth 20 HP on our GT

There. Fixed it. ;)