I'm getting ready to install a 2um Cat filter on the 2007 between the stock filter and the CP3. I'm pretty sure the big line coming straight out the back is the high pressure line to the rail, but not sure which of the other two smaller two lines is the feed/return. It looks like the one looping over the top and going down into the front connection on the CP3 is the feed line I'll install the filter into.

Anyone care to confirm that? Tks....

 

when i installed my airdog it was the line that comes out on top and curves back towards the engine.

 

If you trace the line from the bottom of the OE canister to the CP3 you will find the line you need to replace to add the filter. Its the one pictured above.

 

Yes great, that's what I thought, basically the one closest to the radiator or front of the truck.

Thanks, gents!