in terms of d blue gel,it's NOT stated anywhr dat u shudn't leave d car idle 4 more thn a week.....dis was told 2 my fren(dealer) by his supplier....prolly d supplier had had sum experience whr car being left idle not in use 4 too long d gear oil MIGHT(i'm just guessing here) harden up n turn into sludge in d gbox?d most i've tried is 2 weeks w.out using my car..so far so good......been whacking my car in SIC whnever possible,so far it has never failed me altho i know very well my synchros for 3rd & 4th gear is spoilt.....n dun worry whn u open up d gbox n ur mechanic who 4 d 1st time is seeing d blue gel will comment,"whoarr..y ur gear oil so thick like seasoned water colour 1?"...it's completely NORMAL..dat's how it protects/masks ur worn synchros......so,dun worry too much...........
YRvi,
whn did u start encountering d vibration @ high rpm problem?did any tyre work recently?could b as simple as sum mis-balancing?if not,thn u'd prolly hafta play ard w either ur drive shaft or d inner shaft-joint dat is spoilt.....easiest way i cud think of is 2 get a replacement shaft,install n c wat happens?good luck..........