TR-6's all the way. They are $1.77 from advance auto. Whole set under $16 out the door. I gap mine at .045. (supercharger on car) Everyone says like .050 and up for the N/A motors, but the gap really depends on your setup and the condition of your engine and ignition system. if it is worn, or spark is weak, too big of a gap will lead to anything from less than optimal spark, to spark blow out at WOT. Too small of a gap will result in premature plug wear and poor fuel ignition due to the smaller flame kernel. if its mostly stock in good condition, I would suggest TR-6's gapped at .050. to start.