>I know as a fact, demonstrated in my very own driveway, that a stock
>1.9l exhaust WILL NOT fit directly on a stock 2.1l engine. The oil
>filter sticks out farther on the 2.1l,

I previously put a 2.1 block into a 1.9 van.

I just removed the oil cooler and swapped the pipe that the oil
filter connects to.  (just move it over from your old 1.9)

1.9 exhaust works fine, no problems with oil overheating.

No big deal.