I use orange high temp rtv on my Tygas and have no issues with leakage. If the manifolds or exhausts are worn in the mating area it will obviously make it harder to seal.

Might be worth trying new exhaust springs, if they are a bit loose/stretched they will maybe let the exhausts move more and break the seal easier, the rubber grommets in the frame at the exhaust mounting points also wear and let the exhausts move around more than they should, never a bad idea to change these.