I bought a 98 discovery and had a mechanic swap out the transmission and transfer case.when I went to pick it up it was horrible. The engine idles so rough it hardly runs. It however will stay running but surges. If I press on the gas it bogs down and will back fire by the front of the engine compartment but the car will not move due to lack of power? The mechanics said they couldn't figure it out and pointed me towards the ecu. Now that the car is back home I'm getting codes p1314, p0300, p1316. All misfiring codes I believe. I have replaced the wires, plugs, and MAF. I pulled the plugs and they're black. Any ideas what this could be??? thanks in advance

 

if this is a disco 1 (which it should be since it's a 98) post in the disco 1 forum man.

 

OK thank you