i pulled my ngk plugs out,been getting some popping out the exhaust.i have my timing set on my msd dist. at 33 degree,[bbm heads},as suggested by forum members.i noticed my timing mark is near the tip of the plug,only 1/8- 3/16 from the tip.timing charts shows 2-4 degree too little. what should i do,leave it at 33 or bump it up a couple degree as the pointer could be showing wrong,but its been ok in the past,till i changed ignitions.