All this talk of genuine or aftermarket is just another smoke screen put up by manufacturers/dealers. I think most most of us know that branded aftermarket parts are perfectly safe to use. The manufacturers/dealers are to blame, they instill doubt into customers by telling them that anything non genuine is inferior
Yesterday i serviced a company Vectra 1.8 1998 with 210,000 miles on the clock, serviced by me every 10,000 from virtually new, fitted 4 cambelt kits to it, all aftermarket including service parts and it still runs sweet, also cleaned the idle valve half a dozen times
Its not a question of genuine/aftermarket, but the right maintenance at the right time, and quality of workmanship that counts
Genuine or aftermarket......baahhhh humbug
Peter
PS: If you look at the tensioner and rollers on the aftermarket cambelt kits they are the original branded Vauxhall ones anyway