S1 undertray rattle?

[Pumpkinheeed]

I posted this over on SELOC and have had some good responses on what to look for and what might be the cause.
Just thought I'd see if anyone on here had any thoughts.

Can anyone help...???

I've recently acquired a rattle and it sounds like it's coming from the undertray just below (or near) to the passenger seat.
The car is an S1 111s which has just had a Larini Club Sport back box installed.
The noise appears around 2000rpm then dies away - it's worse on let off of the throttle. It also comes back on ever so faintly just under 4000rpm when accelerating (can't really here it over the noise).

I've had a look under the rear undertray and there seems to be some perishing to the little foam seal along the trailing edge. I also noticed that the two Alan bolts further back which appear to bolt into the base of the Engine Mounts don't have any of the sound deadening foam stuff.

Basically it's driving me nuts...

Any ideas? Any experiences of anything similar?
One other thing is that the twin pipes off the Larini are slighlty out of line and could possibly be touching the rear clam... is this a possible cause?

Any help is much appreciated.

[Gruffy]

I'd check along the length of the exhaust and manifold for leaks that need a quick weld. That'd make a whistle which is easily mistaken for a rattle.

[retrorider]

i have the same car and rattle myself at the moment.my downpipe and flexi are shot so its at ptp next month for a 4-2-1.

[Grinnders]

What ? Don't you trust my advice on SELOC ????

[Pumpkinheeed]

Cheers Grinnders...
Just making sure I get a full spectrum of advice.

Looks like it may be a flexi pipe issue!

[S Works]

I'd have said check flexi as a first check too. But what the hell do I know?

[Pumpkinheeed]

I was beginning to worry I was gonna end up getting a new flex pipe.
But your Paul_c's post over on SELOS gave me a thought... Had a fiddle with the seat belt indicator wire and pushed something under the drivers seat and heard a click. God knows what it was but what ever it was the noise has gone!

Actually come to think about it I now don't have a reason to tell the missus I need to get a full front end system from Larini. Bugger!

Seriously though... if you have this issue it's worth checking... perhaps there is a switch unit attached to the bottom of the drivers seat and it had come loose?

Cheers
Heeed