What is 2001 4 door power/amp usage on stock power system
 

I'm installing 2 amps and I need to know how many amps the vehicle uses stock so I know I'd I need to upgrade. It has a 100 amp alternator now but how much of it is used by the vehicle.

The real question is: How many more ampere draw do you expect from those two amps. Are they a pair of 50Wx2 Class D amps or are they a pair of Orion HCCA amps that you plan on running down to a half ohm? The first option is probably fine while the second one is going to require a battery bank for the 3-500 amp draw if you plan on drowning the neighborhood on a daily basis. I've been running the same Amp sub combo that ironically I bought for my then girlfriend, now wife 19 years ago today for Valentine's day in a stock Blazer for several years now. What specific amps are you looking at and what's the goal, daily drive or competition thumper?

im doing a 4x400 at 2ohms/30 amps for the speakers and a 500 at 2ohms/80 amps for a sub. nothing extreme just something for the drive to work. i have the system in already its not dropping yet but i haven't pushed it. i just wanted to know how many amps the vehicle uses with the 100anp alternator so i know how much i have left for extras.

Well, 80+30=110 amp and you need 8 amps for the ignition system so you're already 18amp in the hole when you crank it up so... the regulator is going to fry sooner vs later. Might want to consider a smaller system or a larger alternator if you feel the need to turn it up all the way. Or, a nice efficient D class 5 channel pulling 60-70 amp max if you want it up all the time.