I was expecting no change and the silencing effect surprised me.

Denis: I think you will find a good result with your plan. I took my cats out as my locality doesn't require emissions after 25 years (78 car) and put the timevalve Euro 'engine pipes' in their place. This freed up some hp, although not much, I'm sure.

I believe 6.3s had an 'H' pipe, so yours may be standard. The idea from what I understand on evening pulses is to get the crossover, whether 'H' or 'X' shaped as close to the engine as possible. Having an X downstream of an H will probably further smooth it out.

Let us know how your experiment goes