1.6 to 1.8 exhaust problems

evening  all
i have had my 1.6 lump taken out and 1.8 put in but now having problems with exhaust/manifold connection blowing like a good un, have used new bits to fit the doughnut and clamps. do i need to change the exhaust or can any one tell me what is wrong please??

its just a pants design, if it was me id bin it and fit a later gti 6 bolt type manifold and downpipe, should free up some ponys as well. make sure its proper git one with a kink then you can fit a roll bar as well

cheers have sorted for now but may well go down the gti manifold road at some point, the main thing is she is now back on the road and running.
again thanks for the ideas.