Manual w/120,000. Just replaced plugs and this seem to help some but not much. You can really tell when the AC is on but it also happens when AC is not on. This seems to happen when accelerating or downshifting. 2nd and 3rd gears, where you really can tell. Hard to explain unless you are in the car. What are some thing to look at? Fuel injectors, maybe run some cleaner? Fuel filter?