I do not know much about the nitro Rustler but my Jato 3.3 has the same problem. After about 55 mph or any speed past 30 mph the front end will pick up and I can never see how fast it realy goes. You said you tied lead weights if that does not work try using fishing weights small and weight allot come in many weights too. Anthor idea is to buy an extended wheelie bar ToweHobbies sells cheap full aluminum wheelie bars and are much longer then the Traxxas Bar. Last you tried aluminum that works but only to a degree switch chaises to a much heavier chiases this should hold it down or switch bodies, I was just runnning my Jato and I lost a body clip I only had 1 on in the front and now had zero, going about 30 mph (body came up not off but enough to trap air) the air forced the car up and made a backflip but landed flat. Buy a cheaper more bulky lexan body instead of the fancy Traxxas trimmed ones.