exhust noise or not

[carlymart]

i few weeks back i had a problam noise i was getting under load
and i was directed to the flexi down pipe
and it turn out it was the flexi and it was it two bits
i replaced the back box with a larini club sport and a sports cat and new downpipe for elise parts and all was well
but i started to get what sounded like a nut and bolt lose and a spring or wire snapping and rattling sound that is getting worse i have had the under trays off and there is nothing lose that i can see and i took the car along the road with out the trays and the sound is still there i have checked all the nuts bolts on all three bits and no problems they are not lose
the car was recently in for a A service and they said the bolts were fine
it now sounds like a nut and bolt rattling and power on and a gasket flapping around when lifting off
it hard to get it to make the noise when the car is standing still
the only rattle i can find is a small noise from the cat when i tap it with a rubber hammer lightly
my Wife will not let me spend any more on it and there for i need to find out what it could be
can some one please give me some ideas on were else to look or any more ideas as i am sick of the car at the moment
its a S2 sport tourer for whats it worth