new to nissans... need a little help

[g-ride]

Alright i just bought my 91 240 last friday, the guy who i bought it from told me it needed a tune up.

here is what its doing.

when its idling, it has an inconsistent miss, if i bring up the rpms slowly it does fine. If i rev it decently hard it starts to miss. When it misses it runs like a car with a really badly clogged catalytic converter.... BUT it doesnt have a cat on it, just the resonator and muffler. Could my muffler be clogged that bad. Also i noticed that the distributer is turned all the way towards the back of the motor. The plug wires look new, and so does the cap.

[d1grandprix]

My S13 did exactly the same thing. Went for a complete tune-up and cost about 250 dollars. No problem since.