some good ideas on this thread, i did the bleeder delay delete when i had my stage 2 clutch installed, as well as the 034 dog bone mount. I agree with both3) Clutch Delay-Valve Removal.
The most popular of the DIY MT mods, as well as being one of the first. The OEM "Bleeder Block" houses a small, greenish-yellow restricting ring that slows the amount of DOT-4 Fluid that can pass through at once. This restriction was put in place to delay the engagement (and diseng.) of the clutch. The original VAG purpose behind such a design is to slow down the clutch feeling in a way that is complimentary to drivers that are sloppy with engagement/disengagement (but becomes a hindrance when attempting fast, precise upshifts). Removing this restriction also removes the forceful "slipping" of the clutch in order to shift smoothly. The engagement point becomes much more pronounced as well. When you replace the stock clutch, it is highly recommended that this piece is removed if the bleeder block is not upgraded.
Instructions can be found here: http://www.vwroc.com/forums/topic/12185-tutorial-clutch-delay-valve-removal-manual-cars/
NOTE: Those advanced with power tools have actually drilled out the stock bleeder block in a way that opens up the channel for clutch fluid to pass through. This is a DIY option for the ECS Tuning Clutch Bleeder Block but I do not recommend such a mod.
6) Engine, Transmission and Dogbone Mounts
People sometimes forget that there are three mounts that work in conjunction in holding our engine and consequent assembly to both the transmission and bay. All can very quickly become soft, wiggly and ridden with excessive play. The two mounts that have the most impact on 6MT performance would be the transmission and dogbone mounts. Now, figuring out which one to go with is a little bit of a hassle, as you must first ask yourself what the goals for the car are. Harder, aluminum-based mounts will create a planted (to say the least) feeling in your forks. This is at the expense of NVH/vibrations in some cases. However, there are many options for aftermarket mounts that simply up the durometer of the rubber/poly (hardness-*ish) by a slight degree. Going this route will help keep gears from wriggling around on you as much, IE, a more stable feeling in the shift-forks. They can also help in reducing the dreaded 'wheel-hop' of higher HP FWD cars. Upgrades can be made to one or all three of the mounts to help plant and stabilize the feeling of gears, bay sway and FWD hop.
Link to a popular OEM+ style option that ups the durometer but sticks with a rubber/poly material (034 density line):
Link to a very popular dogbone mount made of aluminum:
Link to a "dismiss the GF's whining about NVH, I wanna racecar mount. Will prevent majority of tranny/engine sway:
Word of caution: If you upgrade your stock dogbone/ torque arm insert to a stiffer aftermarket design and forget about it for 10s of thousands of miles, more than likely the added stress onto the other two mounts has accelerated the wear of the OEM material.