WC996:
The Wevo mounts and Walrod bushings work extremely well with no addition NVH to speak of. Hands down though the (albeit expensive at $13k USD) regear to custom ratios w/ proper LSD was the most transformational. It's a different car. The engine spools so effortlessly now it "feels" like 50hp was added. The single mass flywheel and RS clutch play a part of course but OMG were my words from first drive after the gearbox upgrade.
Nice! I sent my gearbox in my 911 to Hayden in California, the owner of Wevo, and he personally rebuilt it with all of their upgrades, including custom gear ratios, LSD, shifter w/ Gateshift, oil cooler with electric pump, etc. Best improvement you can make to a normally aspirated air-cooled 911!
http://www.wevo.com/Products/TransmissionProducts/WevoTransmissionProducts.htm
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73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs), 06 EVO9 with track mods. Former: 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550