Hi Andy,
Both manifolds are stock. The pipes and tailpipes had been upgraded to Stage 3 by the previous owner and were completely open along their entire length (massively oversized). They were very loud, with a whip-like noise on the overrun—very unpleasant. With the crossover this negative effect is almost gone. Crossover makes sense for both stock and straight-through pipe system. This crossover can be easily removed for engine maintenance. Crossover diameter is 38 mm.
Cheers Klaus
