Hey guys Im stumped, here’s what Ive got going on. Bent a conncting rod in my wifes 00 Disco 2 with secondary air. Bought a doner truck used the block from her truck and roatating assembly and Non-Secondary Air heads from the doner. Replaced timing chain, oil pump, rings, bearings, O2 sensors and recently replaced cats and mufflers with Magnaflow as my cats were rattling and I assumed plugged causing restriction issues. Plug wires replaced with Magnacor’s about 30k on them.

Problem: Engine is running lean on one side and burnt out 02 sensor. Checked compression 190 high 160 low less than 25% diff so within spec. Replaced 02 sensor that was burnt out starts and idels great, give it gas it studders, missfires all the way to highway speeds. Stand on the gas and the torque converter wont even drop gears, feels like no compression and no power, vehicle getting about 8-10mpg.
Have read older threads will check for vacuum leakes next and re-examine the work done on the exhaust. Any of you with prior experience solving this issue please let me know. Live in SW Minneota any local help would be much appreciated. Final thought don’t suppose the computer needs to be reflashed going from the SAI to non secondary air heads? Can’t remember for the life of me if I swapped out the computers but believe I did.

Vaccum leak
check all connection including the fuel purge valve
block off the nipple for the fuel purge valve and see if that helps
mine was getting stuck open sucking air from fuel vapours
made the truck run like crap and you can smell it wasn't running properly