Alternator stops charging above 3000 rpm's

What is your question?

I replaced the alternator on my wife's 2003 GMC Sonoma 2.2L 2wd truck a month ago and the pigtail wire harness a couple days ago. Now every time the engine goes over 3000 rpm's the voltmeter drops and all the lights dim... Any idea's? Thanks.

What makes this problem better or worse?

Only happens above 3000 rpms

How long has your 2003 GMC Sonoma had this problem?

a few days