I've used the Iridium plugs on my TT setup and ran great. The only problem I've run into with iridium plugs is when using leaded gas. Leaded gas will contaminate the plug and cause misfire problems. I've ran into this problem on the Viper and the Supra with leaded gas and iridium plugs.
As for the brands, I've tried the Denso's and NGK's and haven't noticed any difference on the dyno. The only difference I have found is the price. NGK Iridiums can be ordered at any Advance Auto parts for around ~$7 each where the Denso Iridium plugs are going for ~$12 each.
NGK BKR6EIX - Stock # 6418 - 1 Step colder than stock
NGK BKR7EIX - Stock # 2667 - 2 Steps colder than stock
The BKR7EIX worked out the best for my TT setup. Since I used leaded gas, I ended up going with an equivalent copper plug NGK BKR7E(#6097).
1999 Viper GTS Twin Turbo
Full Weight - IRS - Drag Radial
Built by Drummond Race Cars
Stryker Cylinder Heads / ProEFI Engine Management
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