Ive had my 240z running now for around a year now and it has been doing pretty well. I have a L28 currently and within the past week i noticed a lack of power, more exhaust fumes coming into the car and it was running roughly. The first thing I did was pull each spark plug out to see a change in rpm and Ive concluded that when I remove the #1 spark plug closest to the front of the car there is no change at all. I checked and saw that there was a spark jump, and I looked at the spark plug and it didn't look too bad. my head gasket has been leaking a little since i put the engine in which was probably a year or less ago. could that have anything to do with it. Any help would be much appreciated so i don't have to take it into a shop and pay lots of cash.

Is the number 1 spark plug fuel fouled or oil fouled?

If it's neither, you're not getting fuel which could be the result of a tight valve. Time for a compression check and a look at the valve lash.

is this fuel injected or carburated. had the same issue recently with mine. the result was no fuel, aka bad injecter.