Good to hear that it's improved the flatspot Tbh panel filters don't make much difference at all if any when comparing them. You may get a small noise increase depending on which one you go for but any aftermarket one should suffice. Most people go for one by company preference really. The exhaust blow might be the flexipipes on the exhaust manifold, before the first cat. It's very common for them to degrade and start to blow. Btw the fuel filter only needs to be changed at 144,000 miles as it's part of the sender.
Thanks for the input! Ill stick the fuel filter on at a later date no rush. I'll get car into local specialist to investigate the flexipipes. Probably just go for a k&n or the ktec one.