198 Rods + 2.2L Pistons - advice needed

I have no idea if the coating will do anything to reduce detonation here, but I am rather dubious. There is a lot more to it than just hot surfaces. The chamber here is kinda spread out and not closed, and that slows the combustion process. Slowing combustion tends to increase the likelihood of detonation and a coating would not change that.

I am not sure I follow your comment on the KB's versus 2.2 pistons. Those KB239's ARE for the 2.2L engine ..... ?????
KB Hyper Piston - Chry 2.2L Rod 5.945 Flat Top 5cc 2V [KB239] - $222.46 : United Engine & Machine Co. Incorporated, Performance Pistons

They are good quality hypereutectic pistons, are made for what you want, and the price is not unreasonable. What other 2.2L pistons are you considering?