rudi

hey everyone, i bought my focus 1.8 zetec 3 door 1999 a week ago
due to it not having tax i couldnt test it properly and didnt take it out for a proper run
after i bought it i took it on a motorway, and what happens is
when i press the accelarator down in 3rd,4th or 5th gear after 50 mph the front end shakes but it only shakes when the revs are high and felt quite dangerous, not thru the steering wheel though.
so had the wheels balanced even though i thought it couldnt be it because i would feel it through the steering wheel.
took it back to the trade seller, left it there over night and 1 day after they phoned and said they fitted a new wishbone arm on the left side and they said the shaking is almost gone and reckons if i get the other side fitted it would go away.
so yea the shaking is allot less and doesnt feel dangerous anymore.
i have it booked it at a garage to fit the other side

has any one had the same problem before?
also im just wondering if the shaking would go away fully just by replacing the other side too?

thanks
rudi