I installed a Vetterman exhaust on my Superior XP400 as the Van?s crossover exhaust didn?t fit with the Superior cold air sump. The exhaust was cheaper than the Vans (deleted). However, a number of changes were/are required. The Vetterman exhaust is a trombone design 2 x 2-to-1 vs 4 in 1. With 2? pipes, they are too tight for the tunnel so route out from the cowl bottom (below the nose gear pivot) - more like the RV7, etc. Heat muffs are also different but this allowed 2 muffs capturing from all 4 cylinders. With the tunnel open, more cooling air (and of course not optimism for drag) for really cool cylinder temps. Control cables are also different - I used the open space below the sump - requiring some new brackets but I was able to run the mixture cable on a direct basis eliminating Van?s ?wobble mechanism?.
I moved all this over to the Lycoming - same install. Very happy with it overall.