Bad fuel?

Hey guys, bought a 95 slx with 93,000km. Car rarely got driven by the second (most recent) owner and I'm 99% certain the fuel is stale. He said its barely been driven the last 12 months and rarely filled up. I threw some octane booster in it and 98 to try and bring the number up and it still sputters and wont really rev over 3500.
I pulled the filler cap off before I put the 98 fuel in and it didn't smell anything like fuel. Fuel filter was replaced a few days ago.
Edit: I'm going to pull the tank out tomorrow and give it a clean