Ive had this problem for a while, and was wondering if it could be the rear beam bushes:- let say im in 3rd @ 4k RPM, if i blip the throttle the car jerks forward as expected, but i get a 'squeak' sound from under the rear seats. Thought it was the exhuast moving, but having looked and pushed/pulled it, it doesnt make a sound. Could it be the rear beam? Also, ive had 3 OSR bearngs in 18 months - could this be a sign of bent beam / worn bushes?