In the midst of doing battle with my Super Tigre S90K carburetor I had a stockpile of various branded plugs including a Fox Long Car plug (hot) and a Fox Idle Bar (hot) plug. I tried the Idle bar plug in 3 different engines (K&B .65, TT .46, ST S90K) and none of them would stay running with glow disconnected. The Fox car plug however works rather well. I checked rpms on my S90K and noted a 200rpm drop running the fox car plug vs. my regular McCoy mc59 plugs. If the price is right, I'd use the fox non idle bar hot plugs since everyone's charging $8 or more per plug for mc59's. I can handle 200rpm less if the plug costs $6 or less.