Rattling noise under passenger seat foot well on 172

[enomoosuit]

Has anybody else come across this before??
When I bought the car standard (only 22000 miles) when the car hit between 2500 and 3500rpm the was an awful rattling metal noise.

I had a full powerflow stainless exhaust fitted (sounds sweet) and this seemed to eradicate the problem. The noise has now come back (52000 miles) in the same rev range accelerating and decelarating. It seems to go once the car has been running for about 15mins.

Ive looked under the car for somewhere where a heatshield may be knocking, but ive come up with naff all.

Has anybody else come accross this??

 

[davo172cup]

i ad this the other week, thought it was the exhaust again, had it replaced after 12months ownership, i went to get a S/S system but it was the cat, it was complety fucked, luckilly reno changed it on warrenty as the car had only done 22000miles and it went, but has just come back so took it to reno last week and it is now the brackets on the down pipe? get it to the garage and get them to have a look. get them to check the brackets/heat sheild/CAT etc!
sorry for the essay, hope it helps!