My MBX5 is 3.3 kilograms race-ready (no fuel) with Proline Crime Fighter tyres (each one about 115 grams). Without the body (Team Titan Buggy 2) it's 3.240.
For weight reduction, it has a milled-out chassis, lottaballs, LiPo Battery, drilled out cooling head and titanium CVDs. With Medial Pro tyres it's about 40-50 grams lighter. It's about 250 grams lighter than my last year's MBX5 and I can really feel a difference.
Pictures are on my website.