in which case a 200tdi exhaust from the downpipe back would be a good bet then.
IIRC the ID of the 200tdi is larger allowing greater gas flow.
if this is not the case - i might be mistaken , i usually am , then there should be no issues using a 19j if the 19j is already on and working fine. - actually thinking about it , the steve parker conversion is the restriction in the system.
Im having similar issues - i want a side exit straight through or a side exit with a small silencer but dont want to spend 150 quid on a whole system off ebay.....good chance im gonna hack up and make my own out of bits of 200tdi/19j and various V8 exhausts i have about the place.