Currently I am running with NGKs, which have the temperature value of 5. This is with carbs, runs a lot better than with 6 or 7.

Ah, and I am running those plugs in 2.4T

If you don't need the MSD's rev limiter, you don't need to buy it. However, my opinion is that the MSD rev limiter is better than a rotor one (soft cut limit), and eventually you might save money because the rev limiting rotors cost more. Having said that, I can't remember the price difference on the MSD, and it only comes with 6000rpm and 7000rpm chips, with the packet of 5 at 6200, 6400, 6600, 6800, 7000 being an exorbitent extra cost.

I'd use NGKs too - whatever cross references from those Boschs. Probably about a BP7ES.

Lynn,

I would recommend you try Bosch W5DC or NGK BP7ES plugs for moderate temperature driving, and NGK BP8ES for hot weather and spirited driving. You may have to try a motorcycle shop to get the NGK's, as our 911 cylinder head temps correspond to air-cooled motorcycle engines ... and take similar heat range plugs!

The idle mixture requirements have nothing to do with the heat range of the plugs. Plug choice depends on its operating temperature during engine operation (whatever keeps the insulator/electrodes clean and doesn't overheat at WOT). Adjust the idle mixture using something like a Gunson meter. Choose the normally-suggested Bosch or NGK plugs for your engine. You can also fine tune the plug choice - slightly hotter for predominantly low speed cruising; slightly colder for predominantly high speed driving. IMHO, an MSD or equivalent ignition unit should be able to keep the plugs firing despite an overly rich mixture, but to get the best running engine, you should concentrate on fixing the cause, not the symptom.

Sherwood Lee
http://members.rennlist.org/911pcars