"I bought a longer ground wire because my other was too short. This one is 4 gauge because they didnt have 2 gauge. Is this going to be a problem since my power wire is 2 gauge? Im running 2 Rockford P3's and a T1000BD amp from Rockford. Let me know"
It'll depend on where the 4ga will be used. If it's close to the amp, then not a bid deal, if you're however replacing the 2ga, then figure out the max current the amp will use, and look at the current rating for 4ga. You can always double up on 4ga if you have some left over.
short answer: the power wire gauge depends on two things: current drawn through it length of the wire
for the longer run you may need that 2AWG, but for the short ground lines, 4AWG may be sufficient since the shorter length will generate less heat, which is what we want to avoid.
When you wire that up, i made this mistake and about lost my amps from burning up, turn your music on how u want it, then after about 5 minutes feel wehre u have the ground at and if its hott u have too small of wire