Have / had the engine mounts been uprated ?
***The reason the standard manifold blows is partly because the mounts are so softs - and the flexi's take up more slack than they have too as the engine moves.....excessively i'd say.
Many fit the Toyo after the stock mani starts blowing because of its price compared to new standard mani. And that's 'fine' - if coupled with fitting uprated mounts (re: bushes) at the same time so it doesn't happen again.
But fitting a Toyo 'for the sake of it' to cure the immediate symptom - not the cause achieves nothing as-such. As you may unfortunately be finding out.
Good luck.