Just over 2k rpms? Wow that's low for a 3.4L at highway speeds, these things dont' perk up until almost 3k rpms. With the stick it's really easy to tell; just idle in 2nd or 3rd gear then hold it on the floor. About 2800rpm it starts to wake up. So far it's had plenty of torque for me at the boat ramp at the lower RPMs, but for towing at highway speeds you should probably let it spin faster.

What kind of gate is on your trailer? A buddy has a flat metal mesh trailer that is light, but it's got a 6' tall tail gate made of metal mesh and that thing is like a parachute at highway speeds. If you've got a big gate like that then that will definitely affect your towing. Don't forget that at highway speeds, the weight is no where near as much a drag as the wind resistance. I tow my 2000# boat at 65 in 5th gear and get about 16mpg, so weight wise you should have no problem at all with an open motorcycle trailer. But wind resistance can be an issue depending on the design of your trailer.