So what's the difference if I put on an SLP part vs SLP putting it on? It's the same part isn't it?

 

Yes, but you're not an SLP employee. It's almost certain that SLP has signed a contract with GM that states that anyone at SLP who is going to be working on the SS conversions is fully trained in GM's documented installation procedures, that they know exactly what they're doing, and that there will be repercussions if it is repeatedly done wrong. YOU may realize that you know exactly what you're doing when you install an SLP part, but GM does not, and you have no real way of proving anything to them. So, why should they have any reason to trust that you're doing the work correctly and that they should honor any warranty agreement if you've personally modified your car?

It's basically a trust issue. GM has a contract with SLP that signifies trust between the two companies. GM has been given no reason to trust you. I'm not trying to imply that you're an untrustworthy person, but there are plenty who are, and they would take advantage of GM if GM was less strict about warranty claims.

Now having said that, it still sucks that the dealership denied the warranty claim for the original poster. The aftermarket MAF may have legitimately messed up the cats, so GM is within their rights to deny a claim based on that. I'd take the advice of a lot of the posters here, and put the original MAF back in, and then take the car to another dealer. It's not exactly -honest-, but I'd bet it will work.