Theoretically, the x-pipe will slightly lower restriction from the x-pipe back. The pulse from each cylinder get's split in half at the X so the pressure waves in each pipe don't peak as high even though there are twice of many of them. Much smoother flow. After Green Filters and the X, I have been able to pull about 2 mph higher on the front straight at TWS. Out of 7 events, 5 of them were without the X and greenies. Both of the events I ran after the install were consistant.
Many people say, and I tend to agree, that the X makes the car sound more like a V8 with a 180 deg or "flat" crank. |