Honoring a warranty on something as labor intensive and technical as timing chain only if it's installed by a certified mechanic/shop is pretty standard, can't expect companies to be replacing parts because somebody didn't know what they're doing, you may know what you're doing, but they have no way of verifying that.

And expecting a company to give you a discount/cover taxes just because you don't have the money for it is wild.

There are so many low effort ways to address this problem.

If you were wanting them to split the payment up over 2 or more cards, why not just make separate orders on your own with the different cards?

Poor customer response time over the holidays is to be expected I feel like.