exhaust fiddling

I knew the bike wasnt running right, I had comments that it sounded like a twin! it seemed to have an uneven sound which I was baffled, 2 sets of carbs cant be duff and my jetting cant be too wrong. So looking at reviews on my exhaust pipe work I found the problem which answers the strange sound...not a proper v4 sound that this bike should have. With the Dyno run at snetterton giving a disappointing 77 hp told me why I was struggling so much on the straights, with the mini-twins able to keep up with my acceleration..The poor engine has been struggling...well the front 2 cylinders have strugggled because of how front down pipes connected to the rears. The pipes didnt exactly merge....heres some pictures.....look nice on the outside but on the inside hide the restrictions, that hole is about this size of 1pence coin may be less.