Well $$$$ !!!! New problems with 800. Engine brake, missing and front diff

It seemed all was fixed after the dealer reset it all. We went for a ride last weekend. First thing I noticed. No engine brake, it tried to work one time then stopped.. I replaced the secondary with another stocker cause mine was warped… Put on a gates carbon belt and went back to 1021 primary spring. That’s all I did. So what causes this?

Then I went to to ride it the other day. And now it’s missing and seems to be on one cylinder below 4k rpm. Above that it runs fine and idles fine. Even at times the throttle hangs high for a few seconds then comes back down. Even does it in neutral or park…

Now I’m hearing a clanking in the front diff. It’s not very loud . But it’s there…

Uggghhh, I’m getting so frustrated with this…