As far as TB size, its pretty much based on your HP. No set "rule of thumb". For more accuracy: I was also told not to exceed a flow of 300 ft./sec. Anything over this and your car will feel jumpy at low RPM's. I have the formula for this somewhere. Injectors are also figured by HP and should bye sized at around 85% of their duty cycle. I also have SDS for my bug. Most of my friends with VW's are using it also with no complaints. No goofy laptop needed. Just the included handheld controller. Base systems start at around $700 for FI only and you can upgrade to ignition control, DIS etc. Its more than you want to spend but your getting full programability. My friend is an SDS dealer if you're interested. Feel free to E-mail me.
SDS website:
www.sdsefi.com
The page below should answer most of your questions. Any others e-mail or call Ross at SDS. He is very helpful and will answer all of your questions.
Tech/FAQ page:
www.sdsefi.com/tech.html