I just installed my OSCAI today. I used 2 inch vacuum hosing instead of 3 inch tubing. I cut a 2" hole in the plastic engine guard into which I inserted a rigid vacuum attachment angled forward to collect the air. The 2 inch tube leads from this attachment to the stock air intake and connects with a 2" to 3" coupler. My question is will the fact that I'm using 2" instead of 3" tubing make much of a differance? Seems like everyone else uses 3". Will I just not get enough air going in with 2"? I took the car out for a spin and didn't notice a significant differance. I haven't bought a K&N filter yet though.

 

My opinion is that the K&N filter provides most of the performance increase when doing this mod.

 

2" should provide you with enough flow also.....I am still experimenting a bit though.....