Im looking at rpm service throttle bodies for my all motor gsr im not sure which one will be better between the 70mm-68mm or the 74-72mm. Do any of you guys have experience with this throttle body?

 

For a 1.8 don't go any bigger than 70mm with a smaller throttle plate. If you have a 2.0 or larger, then you might try the bigger TB. I run the 74mm TB on my 2.1 liter drag motor, and a 70-66mm TB on my 1.8 ITR motor.