If you're using one of the AM or FM radios, its important to use the correct crystals and not change the length of the radio or receiver wires, they are "tuned" to work correctly like that.
I would ditch the RTR radios - nothing but problems IMO.
If you want a radio that isnt fancy but has absolutely no problems, I would get the Tactic TTX240 radio system.
Its a 2.4GHz system, and the receiver doesnt have an antenna like most/all others do. I have it, not one single problem and I get nearly too much range - I can barely see it down the road and I still have full control.
All that for less than $100.
Car-less (Velox V10 or 733) // RB T10.5"+" (JB Modified) // Bluebird BMS-990DMG (St) & BMS-631 (T/B) // ATS 16% // Capricorn Wheels // Protoform
"70% of the time, it works ALL the time"