i had my friends shop do it for me as they cleaned out my UIM at the same time. trust me take it off. mine was just filthy, black stuff just packed on there. pretty gross. i wouldn't do it without taking it off to make sure i get both sides spottless.

Black '98 Mystique V6 atx. superchip,2 1/4" SVT style dual exhaust (custom) with no cat, high flow res, flo-pro mufflers with Ractive tips, 8.5" K&N conical with CTA adapter, UR Ultra Street Pulley, TH-fix. 215/45/17 Bridgestone RE730's on Konig Absolute wheels. Trans go Shift Kit, High stall torgue convertor, 24000 BTU transmission cooler.