More power for TE 250

My '07 TE 250 needs more bottom end (in my opinion). I've re-jetted it, cut out the restricter in the muffler, went to a 52 tooth rear sprocket, etc. but I'm looking for more low end pop. Do the aftermarket slip-on mufflers make that much of a difference? I've ridden a couple '08 YZ 250F's and they seem to have a lot more grunt at low throttle. Up top they're the same as my TE, but since I ride tight East Coast woods I would like more low rpm snap. I don't want to go through the time and expense of a big bore kit at this time. I want to max out my 250 first. Options anyone?

I have a Doma exhaust that made a noticeable low end difference but it's a bit loud. Fran at Bottone's does a mod that is different than the online mod-you could check with him. I went with the 300 kit-made all the difference.

Sounds like a big bore is the way to go. Not sure if I'll do the 300 Athena kit or the FBF 270. It will have to wait for now.