E36 328i loss of power - exhaust?

[jac-in-a-box]

Long story short....kids P&J was whacked up the rear, body damage perfectly repaired but the exhaust is giving problems.

Shunt caused exhaust to move forward and wrote off rear box. Exhaust blow evident from engine bay but couldn't pinpoint from where.
Insurance assessor agreed to replace rear box (genuine BMW) and re-joint remainder of system.

Re-jointing sub-contacted out to BMW specialist who only went as far as the manifold to front section pipes and returned car with the blow still loudly evident
- suspect the the manifold to head joints, or one or both of the manifolds has cracked/split.

Car also now suffering from heavy fuel consumption and lardy performance.

Is an exhaust leak likely to cause this?

The car will not, AFAIK, pass an MOT and it's potentially dangerous...fumes being drawn into vent system, that's the line I'm taking with insurers.

If insurance won't play ball - a lot of wrangling with insurers to repair rather than write off; any good sources for used manifolds? Are these manifolds prone to cracking in normal use without being thumped up the rear?

Main repairer is sympathetic to the situation - it's the insurers who will be difficult I suspect.

Thoughts, advice on the fuel cons/performance issue welcome as are any ideas on how to persuade the insurance to sort this out.

Thanks

[blackspider]

possible the cat is damaged and turned restricting the output.

[jac-in-a-box]

blackspider said:

possible the cat is damaged and turned restricting the output.

Thanks...turned?

Emmisions test will confirm, or is there another way?

[blackspider]

[quote]

Thanks...turned?

The catalyst breaks up and the honey comb turns on its side-the exhaust gases cant then travel down the exhaust.

It may or may not show on an emmisions test-the engines are so efficient they can run without the catalyst.But if you bang the cat with your hand you may hear it rattle-A diagnosis test should show it via air mass.