bazzer

I have recently bought a 2.1 v6 done 66000 miles,fully serviced but recenelty when I accelerate hard i get a slight misfire It doesnt stop the car accelerating seems more like a bit of fuel starvation or pinking,sort of thing when the leads arew a bit damp which they arent as its stored dry and i have checked for water and condensation I was advised to put some fuel cleaner in the tank which i have done but has anyone got any thoughts on what it could be