I don't know about the sprinkler reducers, but the duratecperformance(draxas) adapters are a perfect fit. I used one of the 70/75mm adapters on my duratec to make a CAI and they're just a PERFECT fit. If their CAI was available back when I had a bug up my a** telling me to get a CAI, I would have bought one of theirs instead of making my own. I spent ~$200 relocating the battery and custom fabbing with junkyard parts and duct tape.
If their CAI kit is as nice as their adapters, you won't be disappointed.