If your carb mixture is right, and you still get dusty black plugs, then yes, the need for a hotter plug is indicated.

But make sure the air-fuel mixture is correct first. One of the those a/f gauges should help tune it.

I haven't really learned how to tune with hotter/colder plugs, I've always used the "stock" NGK V-grooves BPR5EY-11 (6937's?) and never had a problem. I did recently change to Denso Iridium IW16 plugs, and opened the gap up to .050" cause I'm using a 210 distributor, MSD 6AL, 8.8mm race wires, and Accel Super Coil. Opening up the gap on my Buick 455 V-8 after I put on an MSD box made a noticeable change in power, but I haven't noticed anything too different in the A15.

I read in the manual that if your plugs burns like a dusty black you need hotter plugs any of u guys know what they mean?Or have you guys got any tips on what plugs to use?