Haha, I went through the same thing a few years back with my 1100. It was my first gun, and this place wasn't around.
I had the same issues. Mine is a 3" magnum, and light loads wouldn't cycle for sheit. So, being the rammy little impatient bastard I am, I tried to drill a second gas port. Ended up breaking off the drill bit, and had to send it to a machinist friend to drill it out. I still have the barrel, which now has TWO gas ports, but never got up the nerve to shoot it.
I ended up buying a new 2 3/4" - 3" barrel from Russel Sports ($300 at the time) with Rem Chokes, and now it cycles everything. The port is slightly bigger on this one that the original.
Seriously, if I could do it again, I would only SLIGHTLY open up the gas port on the 3" with a slightly larger drill bit, and give that a try. If you're gonna end up getting a new barrel anyway, why not try it?
The only downside will be that when using 3" shells you will be uneccessarily hard on your internals, due to the increased gas flow. It might hammer back on the bolt faster than before.
Either way, I would try opening the port first, and if that don't work, just buy a new barrel.