1992 Nissan 300ZX Rough idle

My 300 has a rough idle. I bought it a couple months a go. It has never cut off. The timing belt was supposedly already changed. I had the plugs swapped. I am sure there are sensors galore on it. I was curious as to what the biggest complaint on this might be and what the fix could be. It idles low I think, prob 650. It bounces sometimes. Of course oil pressure is low while this is going. While in park, it seems to have a miss in firing or something. You can hear it in the exhaust. You can feel it up to prob 1200 rpm. When driving it seems to run fine, no problems at all. Still get pretty good gas mileage. Would love for it to run smooth. It has very low miles esp for the year.