ArkBird96

yeah those things are a PITA to replace on LS1's at least. Particularly the passenger side valve that I had to replace to pass emissions as it was throwing the P1416 code. I had to use a PVC pipe on the wrench as a breaker bar to get enough leverage to get it to even MOVE! Plus, the fact that the throttle/TCS cables are right next to it and kept getting in the way didn't help too much either. I think I also used some Liquid Wrench to help get that thing off there. Getting the old one off is the hardest part IMO.

ZexGX

iTrader: (28)

What I did for my passenger side one was to remove it off the manifold and place one of the wrenches in a bench vise, then with one of my hands hold the check valve in the wrench that was being held by the bench vise, then had a friend hold the other wrench, then with my free hand use a big hammer on the wrench that was being held by a friend. By doing that, a few good whacks was all it took to break it loose.

ZexGX

iTrader: (28)

I just went to Autozone's website and an actual Autozone store. The part number previously mentioned is not available. I'm guessing it's no longer being made? I went to Kragen Auto Parts and they had only one. It is made by BWD and the part number/name is CV8 ($14). It is a gold color and looks quite different externally from the OEM GM part, but it should bolt up just fine. I had Kragen place an order for another one so at least the two check valves will match in my engine bay (that, and I know they'll both work). I had the clerk at Autozone cross-reference the part number but as I figured from checking Autozone.com, nothing is available to purchase nor is there a way right now to place an order for one.

RockAuto.com has the OEM Delco units for $26 + s/h: ACDELCO Part # 2141045 {#12565503}
and also one that is the same as the BWD CV8 that I bought at Kragen ($10 + s/h): STANDARD MOTOR PRODUCTS Part # AV7

Formula413

iTrader: (1)

If I look it up under my car on Autozone's website I get Duralast PN# E204, and it says "not available". I guess they don't carry it anymore. Advance's website shows the same part listed above, CV8.