Probably .024" is way too much gap for that cold of a plug. Try .021", or you may have to close it down to .020" This is a really cold sucker to be running on a DD that sees any amount of idling with that much of a gap...it was bound to foul in no time.

I run BR8ES's at .023", however my brother suggested opening up the gap to .028"which he said would give an ideal spark, but he warned me that it might not last long if it was idled for extended periods. Sure enough it fouled on me after 500 miles.

At the time, I didn't have another set of new 8's so I pulled the fouled plugs, cleaned them and regapped them down to .023" Now. I avoid all idling after startup and at traffic lights and do mostly high speed highway driving. I shut the engine off at red lights, etc. So far, the same cleaned and tighter gapped old plugs are running flawlessly with another 1000 additional miles on them now.