I had headaches with the exhaust system as wells It was so badly designed that it destroyed my catalysts because of the collusion of the gases.

Now I believe I have ended up with the best solution about the exhaust :

Tubi silencers which do not communicate and take out the exhaust fumes from indepedent tubes. The silenceres are only connected with an upper tube which acts as a silencer and then the gases come out separately. This way I have less resonnace and more peak power.

With the clutch though I am a bit troubled as 10.000km (6-7.000miles) is too low mileage for a clutchs' life. OK I am driving a little loonetic cometimes, but I was driving the same loonetic when my car was OEM and with the OEM clutch I had done 30.000 miles without even thinking of changing clutch!