On my car I have a full mongoose system , however it has a few problems !

The joint between the downpipe and exhaust is blowing but has been welded together therefore needing replaced.

The centre box/silencer has been bashed off speedbumps so many times that is is blowing.

The sleeve on the end of the tailpipe is rattling , which can easily be removed.

The bore of the exhaust is 2.5 inches , where the manifold and downpipe is 2. Will this lose me back pressure ?

To sort the above I have been quoted £95.

Do I have it sorted for the above , or but a full brand new magnex for £245 ?