engine replaced and exhaust red hot

Running very low on power, has this rattling noise, Im wondering if something was not connected when
i put all the harness together. the engine sounds better than old one generally quitter.

Here is a picture of the exhaust, looked into the cat it seems like its there can only see it from the sensor hole.

If you shake the cat does it rattle?

if it has new cats then it should not really rattle.. plus the big thing that has changed is the engine..

sounds to me like the engine is not happy.. maybe the timing on the chain is wrong.. maybe there is damage to a valve... really the cat would only ever get that hot if there was combustion taking place in the exhaust so sounds reasonable to think that fuel is not getting burnt when all the valves are shut..

sad fact is if this is the case could be that the cats are knackered too as they are not built to be burnt!..

Unbolt the center pipe from the cat and see if it glows as it may be the other part of the exhaust blocked have you put you hand over the tail pipe to see if a lot of gases is flowing out

Have you checked the spark plugs? if its pouring fuel through then they will be very wet and sooty. Have you got any fault codes, last time I looked at an M13 with a blocked cat it was throwing a bunch of codes, including MAP and IAT.

Where are you located as it dont say in your profile there may be some one close to you that can help