I've made a few mod to my TOM, first was a nice spool feed for the plastic
Image of TOM printable spindle for 5lb spools - Thingiverse
the second was a new driver, had a real problem with the filament stripping when the print I was working on need to do a lot of reversals (damn near everything LOL)
Image of Mk6 extruder drive for 1.75mm filament - Thingiverse
made a huge improvement, a bonus is it's easier to change color now.
Thingiverse is a great resource for projects and ideas, there are a lot of sharp people working with these things