Does anybody know what Cold air intake size would fit in my 03 LS 3.4 L?

 

Any of them should bolt on. ZZP has some, you can even get them on ebay for the 3.4 but they are the same as the 3800's as far as I know

 

I made my own with aluminum tubing and a couple of fernco couplers. The stock intake is definitely not the same as the 3.8, having been around each of them. I dunno how you'd adapt it.

The MAF on the 3.8 is directly connected to the TB...
The MAF on the 3.4 is not connected to the TB, instead it's in the middle of the intake pipe. This is why I connected my DIY bumper intake to the MAF and kept the stock tube between the MAF and the TB.

 

Thanks for the advice you guys I just want a ton of HP