I've had the RS192 on my car for over a year now and get a metalic "tinkling" sound at high rpm ie, when booting it. I've ignored it thus far, but took my car in for an MOT recently and failed on very high CO and HC emissions. Looked under the car and despite it being sealed with copious amounts of firegum, there was a lot of sooty deposit at the join where the center section meets the pipe for the rear boxes.
So put the car up on jacks, took out the centre section, sanded off all the old firegum. Drank a can of coke, then took the can and cut the ends off. Trimmed the roll of metal to about 3" wide and used this as a shim wrapped around the end of the pipe of the centre section and inserted it back in to the pipe for the rear boxes. The fit was much tighter and used firegum to lubricate the assembly. This time I also used the car jack that came with the Clio to support the weight of the centre section to ensure the system was as straight/aligned as best as possible before tightening up all the clamps.
Done a couple of hundred or so miles and so far no leaks, no sooty deposits around the joins, no tinkling noise on hard acceleration and it also passed its MOT (most likely thanks to the Italian tune-up before the retest!)