Just woundering why my subs are making a whining noise when they hit low bass but when there just playing with minmum bass there is no noise ? any suggestions!

maybe a grounding issue? maybe you don`t hear the noise cause its turned down. what ga cable do you run? more details please.

Well the amp is only im using 4 gauge the amp is 800watt rms so that should be fine rite?

do you hear any noise when you rev the car?

Is there a stiffening capacitor in the system? Is your battery lead acid type? (with caps)
Check the voltage your amplifiers are getting when there's low bass at high level.

No there is no capacitor should i need one and im not sher what kind of battery it is.

I'd recommend a stiffening capacitor for any system pushing over 500 watts total. (this will HELP the system, not cure the problem)
Ask your mechanic what type battery you have.