Question on servo's.
 

In terms of throttle and steering servos, is it okay/safe to run two different brand name servo's for each action?

Bought an XTM XST rtr kit about a year ago. Has siruis servos and the 24.7 engine in it. The steering servo died and I replaced with a "hitec" I believe it was, and have had zero problems. Now couple months later the throttle servo has gone south. Replaced it with a fubata.

What I have noticed: It will make a twitching sound when its sitting on the floor with the reciever on. If I turn the reciever off, it will stop twitching.

I have probably a good 80 ft of range now and the car will loose complete control. Where should I start, or should I go back to the first question?

Running different brand names is not a problem at all. The twitching sound may be the servo always looking for center. It is very common in digital servo's but can happen in analog. What servo is it? But to be sure, check to make sure there is no binding in the steering assembly.

the two problems are not related.

q1. Yes you can run different brands of servos

q2. try re-binding the tx/rx and make sure that both tx and rx batteries are fully charged. Most of the time the rx batt is the culprit it may show even on a multimeter that it has good voltage buy under load it will go below the threshold to keep a good signal range.