The gains are awesome IMO.. I gained a lot of power and fuel economy off of this setup..
I used to drive around with 300 miles per tank, my last tank I went 350 off the streets and I can get over 400 for freeway driving..
Its a good setup.. One problem is if he uses this setup:
Then he will need more hood clearance, if he uses the GenII without the stock intake arm, or without that black mount peice then he can use stock hood, but it doesnt make as much a difference without the entire GenII setup.. I used to use the stock intake arm and I didnt get the fuel economy as good as I do now, or the power that I do now..
IMO it was one of the best upgrades I have done along with the MAF mod with these two mods..
I thought the K&N Gen II was a good mod that yielded noticeable power gains and better gas mileage. Honestly, though I was not impressed with the TB spacer. I noticed NOTHING when I installed it on my truck(cept for the whistle). And Zombie's right, you can't use the stock hood if you want the Gen II and the spacer. Some say leave the black mounting ring off, but I'm not sure what holds the damn thing on if you do that.
Well I can say that when I was using my stock hood I had the GenII and the TB spacer on at the same time.. Only dif was I was using the stock plenum arm from the stock intake and it fits, but I want to say one thing.,. That plenum arm doesnt even compare to the K&N arm.. When I finally got my cowl hood I put the GenII plenum arm on and it upped my gas mileage by at least 50 miles per tank.. One thing I would recomment to anyone is get rid of that stock plenum arm and get a different one.. It will make a world of difference.. That is why I didnt get an Airaid.