I have an 01 EX 4-cyl 5-speed with 146k. At 50k to 70k, it shakes very bad when trying to accelerate. This condition is even worse when going up a hill. When just cruising at this speed, vibration is noticeable, but not bad. It doesn't seem to be tire/wheel related as I just put my winter set on and the problem persists. It isn't rpm related either. The problem occurs in both 4th and 5th gear. Any ideas on what could be causing this?