I honestly could tell a difference rather if it was the DP or the complete system...it runs better and has great throttle response. The rest of the Xj is stock so this is the only performance enhancement ive made. Both my and my brother have 97's, mine with this exhaust and his with factory bend and mine would run off and leave his and mine has 31 mtr's on it.
Just common since tells you if should be a benefit. Anything that is blocked off / pinched wouldnt breathe as well as a open chamber like this. Shoot for 60 dollars, its not like you would be wasting money or anything.