I don't know that there is one on a 1998 FLTRI. The manual makes no mention of one, and the drawings in the service manual do not show one. There is a number for it, 32495-98A. There is a mention of a kit with it for a side car. I have had mine on its side while running and it did not shut off. Looking at the drawing for it I would guess that it is attached to the side of a bracket, possibly in the fairing.

Have you looked for an intake leak on yours? Backfiring usually indicates a lean condition.

 

Originally what caused the bike to start running bad was the head temperature senson however. I was told i needed a n ecm to. so I found one on ebay. bought it and tossed it in. welll.... long long long expensive story short. the Ecm I bought is the wrong ecm. It is off a a 99 electra glide. which uses a diffrent b bank angle sensor and diffrent rectifier. . this ecm is not providing any voltage to the red wire on the cam positon if I jumper 12v to that wire it runs perfect. but engine light stays on and still throws a code 44. I need a magnetti marelli ecm off of a 97 or 98 bike then my problems will all go away.