I wanted to know if anyone knew how to tell the difference between the PV1 and 2. Markings? Size of inlet/oulet? Physical size?

I bought what should be a PV2, but it only has PV on the side and has 2 1/2" inlet/outlet. I thought I saw a pic on the site before that showed one with "PV2" on the side.

One other thing, what is the difference between performance/horsepower gains of the two?

Tried the search function, but didn't come up with anything definite.

Any info would be greatly appreciated. Thanks.