since I put a cai on my truck I've noticed a hollow type noise coming from the air filter area while I'm going slow at very light throtle. I thinking this may be from the exhaust back pressure valve closing but it only does it some times. I'm just wondering if its normal or if anyone else has experienced this.

 

I assume this is when it is fairly cold outside and goes away after she warms up? Then it's normal and is the EGBV....

It's all good...