I run 3923's on my TW Heads. Haven't had the car under a full load of boost, but it has seen many bottles of nitrous and the 3923's. Trick flow recommends the 3924's as a stock style plug for the TW cylinder heads, when adding boost/nitrous i would recommend going w/ the 3923's. Don't go any colder than what you have too. Same goes for plug gap, the wider the gap the better the potential to ignite the fuel mixture, only go as tight as needed.
93' SSP Notch 579hp/556tq - SOLD
00' GT 641hp/536tq - Novi 2K(17psi)