I just bought the car and do not have prior.

I just bought the car and do not have prior service records. Approx 170,000km on the motor.
98 acura integra gs. Timing belt replaced 20,000km ago. I just replaced the spark plugs to NGK iridiums and they are gapped to.044 as per spec, new fuel filter, the car has a high flow exhaust system. It is pulling code 74- random misfire on cylinder 4. Looking at the spark plugs it appears to be running lean. I have 87 octane fuel in the car currently.

Car was sputtering and idling rough after 300 kms on the highway today. After starting it 6 hours later it did not sputter but I am still getting the same code.

I do not have a timing light to check with, but after reading different articles I believe that it is advanced beyond spec possibly causing it to run lean?
Any suggestions of how to fix this issue?