Sorry but I have another question  . My exhausts appear to have restrictor plates in them, one has clearly been badly drilled.
Should they be there or should they be open?
 

Should be open, maybe someones neighbours moaned  That can't be doing it any good at all

Those look a bit if a restriction the exit hole needs to be the same diameter or larger than the inlet  if you want more performance a bit of back pressure is good but the engine needs to breathe freely   

That's another thing on the list of previous bodgery then 
I'll be removing them straight away.
Thanks guys