recently, MY 93 G20 engine nosie 's getting louder, especially when I accelerate. its mileage: about 140000 kilometres. Dose some engine treatment additives useful? And another problem is idle shakeing, when I step on brake to push to parking or waitting for red light, the car's shaking, I changed spark plug and ign wires totally, still shaking, but drives no problem, I took it to some car repair store, they didn't solve
the shaking problem, dose anybody have idea to help me?

Thank you.

Noise: what's the state of the exhaust system?

Shaking: what's the state of the motor mounts?