when i start up my rexo, it revs up to 2 and then drops to one and keeps reving back and forth til like 5 mins until it warms up. i just want to know if this is normal, because my other friend has the same problem

 

its the advanced warming system....it does this to get the engine to operating temp faster...its normal

 

The AWS won't make it drop and rise, it only gives you a faster idle for about 20 seconds to warm up the cats, can be defeated by starting the car in gear.

If you idle is fine once warm probably not a big deal but if not check TPS, vacuum leaks, etc..

 

After the initial 15 second warmup, the ECU limits closed throttle RPM to 2000.
If anything pushes it higher the ECU gives a brief fuel cut.
(Now you know where the Mazda zoom-zoom theme come from.)

I suspect either a vac leak or the fast idle cam adjustment is a little high.