Good morning looking for some advice. My 02 forester has a misfire code on cylinder 4 when you reset the ecu it takes about 150 miles to come back. I've put new plugs wires and a coil pack on it and still have the issues any advice on what may be causing this ?

What did the no. 4 spark plug look like when you pulled it out?

How many miles and years on the spark plugs and wires??

Something else to check when all the usual obvious stuff is not the problem is the seal around the spark plug tube in the side of the valve cover. Sometimes that fails and lets oil get on the plug. Wet plug=No spark. Pull the rubber boot for the spark plug and check for oil.

I don't remember what it looked like and I don't know the mileage the previous owner had lied a lot about the car to me. I have put new plugs and wires on it in the last 1000 miles and still get the code I can't remember if there was any oil on the old plug wires. I don't think there was but I'm not even sure if the last owner put on a new coil pack either to be honest

I had a 99 Forester with the same problem but on #3. Did everthing  you did but still had the code. Turned out to be a burnt exhaust valve.

Try thr dollar bill test. Get the car warmed up and hold a dollar bill in front of the exhaust pipe and if it grets sucked in and then out..probably a sign that the exhaut valve is burnt.