My 93 landcruiser just hit 200K Miles. Lately the tachometer has been bouncing between 900 and 300 rpm's while idling in drive at stop lights, etc. Off the line there is hesitation. I will give it gas and it will move slowly. Once rolling it will pick up with a normal acceleration curve. Additionaly, at about 40 mph and about 1200 rpm's when I am coasting and gently give the engine gas, the engine will start to shake violently. I have been to two dealerships and they are unable to find a problem. I have replaced plugs, wires, cap and rotor. The computer is not spitting out any code. Check Engine Light is off. Any suggestions on what to do? Anything will help. Thanks, Adam