[niles]

MG:

Keep looking you haven't found it!
When the body is off; find the centerline of the chassis(CC) by measuring mid way between the suspension uprights; don't measure the front brake rotors. With the car on even jack stands, pumb or use a 4 ft level to make the edges/CC on the floor. Rear CC can be found by determining a CC off the rear rotors. Next pumb pob off the edge of the heads to determine if the engine is at the center; some of your evidence would suggest it's not. Mount your pipes to the headers and find out were the problem is. EM uses the flange joint; if one of them is not welded on the proper angle it can throw everything off. Just keep looking and thinking; you just haven't yet ID'ed the problem
gn