The stock K&N rubber adaptor that hooks to the MAF is a pice of crap on my car. It never properly clamped to the MAF and one could easily pull the MAF out of rubber adaptor. So, I went to Home Depot last night and found a 4"-3" pipe adaptor made to connect plastic to metal pipe (I believe). The problem is the inner diameter for the 4" side is actually 4.5" to compensate for the thick plastic pipe it would be used on so it will clamp to the K&N CAI but it has to be clamped down tight, very tight.

The question: Do y'all have any other recommendations on a rubber adaptor with a 4" inner diameter on one end and a 3-3.5" inner diameter on the other?

 

I bought a rubber coupler at a semi truck parts supply house, It was actually for a semi turbo charger and it was the perfect size and all.