first off yes they do fit with SOME CAI's, some that have different dimensions MAY not fit, all the TBS does is aid the air/fuel mixture in atomizing much more efficiently, which creates a more complete burn in the combustion chamber resulting in better fuel efficiency. so yes they do help some, not a lot, but some, accompanied by a CAI and exhaust you will notice much more difference than on its own. so they are not "as useful as a box of rocks". For the record, i am running a S&B CAI AND a Airaid Poweraid TBS on a 07 NBS silverado, and both fit as well as work very nicely together, already noticing an increase in fuel mileage and power, will let you guys know more when i have gone through a few tanks.

Try them first before you knock the product.

 

I used a Helix power tower TBS on my 89k5 with the TBI 350 and low end throttle response was better. MPG i couldnt tell becasue i believe the k5 for that year came with 235/75/15 and i was running 33x12.50 tires so my odometer was probably off. it would consistantly get 9-10mpg city driving with factory 3.73 gears.

i have read about the tbs on another forum and most there seem to like it. most have stated that the tbs hasnt help out as much on the new ls motors vs the older tbi motors, but that it helped some. im looking to get one but with my K&N series 63 intake i dont want to hear the damn whistle. it annoys me. so i havent decided yet.

 

i havent noticed any whistle at all with the one i purchased, may be because i used all the gaskets and torqued everyting, but there is no whistle at all with mine. check out the airaid poweraid tbs. every vehicle that i have personally seen them and heard them on has not had the "whistle" that everyone speaks of. Good luck!

 

whistle while you work. ....... .......