I have a few GMS mufflers I would keep as an upgrade in performance for my OS engines. I like the larger chamber and omit the baffle with the swap. I've noticed a gain on the tach doing this. GMS mufflers were the poor man's Ultra Thrust. I never liked the tuning issues with GMS or Tower products. It was quite hit and miss in quality.
The carb is completely different on the Super Tigre engines. Consistently, I've seen more power from a Super Tigre engine than any other in it's category and price range. I run the 45 ABC Tigre's with 10X8 props and tach as well as the OS AX 46 that has a 10X7 prop. You can't beat the price of a Super Tigre. Many like the Thunder Tigers, but I again found bearing issues with those, while my Super Tigre engines go for years without requiring any repairs. At least this has been my experience in recent years, exclusively flying glow powered planes regularly.