Hi Dave, if your bike is a DT175A the correct standard jet would be 150, you are running a less restrictive filter so that will require a richer jet, say 160. Also air density has an effect too, high altidude and hot dry climates etc also have the effect of richening further. I would go for the 160 first and do a plug chop, put the needle back to the correct clip position. jets aren't expensive anyhow so you could even buy a choice of the sizes