Check for clutch chudder.
http://www.vstrom.info/Smf/index.php/topic,7503.0.htmlIf chudder is the cause of the problem, you need to get out of the rev range that causes the problem or see Sharealike for a clutch fix.
A sprocket change will change the rev range you are in at a specific speed. It will not affect the feel at 3-4k rpm but the speed. The idea would be to lower the gearing so you get over 4k rpm or simply downshift.
Typically, the cause of 3-4k rpm running issues is the fueling is too lean. Getting above that range or changing the air/fuel ratio at that rev range will work better than a TRE which has its biggest effect at very high rpm. A TRE may be enough though and is much cheaper that a Power Commander. Changing the low range to a richer mixture can also be done with a Yoshi or Teka box that rewrites the stock ECU settings if you can find somebody with one.