The blog below tests a Mazda 6 turbo on a dyno with same mods on the same day with different intake air temperatures. At 66 degrees it produced 262 WHP (smoothed value) with boost pressure dropping from 20 PSI to 18 PSI. At 88 degrees, it generated 230 WHP (smooth value) with boost pressure dropping from 20 PSI to 16 PSI.

http://stratifiedauto.com/blog/the-e...rged-vehicles/

 

That is from ECU compensations, not the actual pure effect of hotter intake charge...

 

20* should only be about 15-20hp. As razorlab said, the ECU is also doing other htings in the background reducing power. Likely less timing to go with lower boost with the higher IAT's.

 

and obviously boost. 4psi from a 20* charge temp change is a compensation for sure.

 

It was only a 2psi different out the top though, 16 vs 18.