just to share my experience...
ive been suffering the gear problem 4 moth back, my case is i have problem with gear 2 and 4 shift, btw im using b5 gearbox with 2 piece of dshaft.. from what my fren say, it is caused by syncro problem. so i just ignored them as i think its not a big deal.. but the problem rise again after i tekan until 200kmh, i suddenly heard something noisy at the leftside of the engine... i slow down to 100, but when i try to speed up again, there's a trrrrrr sound and its really loud.. i press the clutch and the sound dissapeared.. so i shift to the 4th gear, the sound dissapeared, but after that i cannot shift to the 5th gear or freed the gear..when i go to the mechanic, he said.. say bye bye to your gbox...uwaaa.. he said because the gearbox is short ratio (5th gear rpm 3k = 90kmh) i had push the box over its limit..thats the problem...now had to replace gbox leee

so bro better check ur box