NB, I'm using basic tools.
The most advanced tool I have is the MIG welder my wife bought when it was on sale at Lowe's. Everything else is basic stuff like belt/disc sander, hack saw, Dremel, and time.
Got started on the exhaust.
The 2 in 90 degree EMT will be used as a sheath over the stock exhaust canister.
Used some masking tape to wrap a straight line around one end of the tubing. Placed the tape as far towards the bend as I could. You'll see why soon.
Used a hack saw to cut along the tape...
...then flipped the section I just cut off so it can be attached to the opposite end of the tubing.
Went around the joint with the MIG welder, tacking the two pieces together at random places.