X pipe H pipe or side by side

Some people just can't physics.. Even if it's 2 into 2, the 2 exhaust pipes are still carrying momentum of the exhaust gasses and applying an increased scavenging effect to all cylinders rather than 'waiting' on the same-side cylinders to do the work.

Run without one if you like, those that have them seem to see plenty of benefit and have timeslips and dyno sheets to prove it. Claim all the quotes you like, they don't change the numbers.