Denso spark plugs?
 

I use to buy 4 ngk's for $32 Today I found some Denso plugs for $24 my question is this, are the Denso plugs any good? Which one is the trailing and which is the leading? The plug #'s are as follows S-31A 3111 and s-29A 3106 the guy at the parts store had no Idea which was which if any one could help that would be great

Denso also makes OEM parts.

http://www.densoaftermarket.com/onli...ZDA&model=RX-7

http://www.sparkplugs.com/results_ap...1&AAIA=1192328

From the Sparkplugs.com page,...ASSUMING that the NGK BUR7EQP corresponds w/ the DENSO S29A-3106, the NGK BUR9EQP should correspond w/ the DENSO S31A-3111

This is TOTALLY an assumption. My suggestion would be to either call Denso (1-888-96-DENSO) and ask for their help, possibly in their aftermarket department.

You can also call Sparkplugs.com to further verify the info.
888-800-9629