vibration!!

[Laur]

Guys
I've got a 2003 clk 270 cdi 55k on the clock full stealer history it has a vibration at 60-65mph that seems to come from middle of car could be gearbox prop shaft.The stealer had a look and wants to replace all the injectors!!!! but won't say for sure that will be a fix ( nearly £900 for job) Wheels have all been recently balanced.

Thanks

Laur