hi guys new to this 

i have a 53 forester xt which has developed a nasty vibration under load over 55+mph 

my garage has test driven along with me and we have tested and changed several parts (which were worn/faulty anyway) the items tested or replaced or checked are:- all bushes , mounts, bearings, tie rods,ball jointssuspension,drop links there seems to be no excessive play in the propshaft or cv joints .....me and my garage are at our wits end ...someone else must have come across this problem before ...if  anyone could help i would be very grateful

any idea on location of vibration ? front middle or rear . how vibration felt, through seat, steering wheel etc etc ...

does vibration stop as soon as clutch dipped (assuming manual !)  If goes instantly it pretty much illuminates suspension related and points towards drivetrain .