i had a similar problem when i got my skunk2 im but my idle was surging and a couple times sticking. I beileve itsyour tps voltage on the back of the tb, im sure it needs to get tuned. Well in my case i got a Jg tb right away and it basically fixed the problem. As for the gains of your ITR tb it's 65 mm right well that the same as my JG, the gains i felt were lots of extra throttle response, is a fun mod.

:edit: If u get your itr trottle body u will need th ITR cable bracket too, this make the cable run horizontal, in stead of at an angle like the GSR's