Feedback/alt whine sound after install

[Alc5M 10+ year member]

Someone help me out here

i got an 03 tahoe with stock bose system, non premium

deh-p4000ub HU and GM-os04 harness

I installed the headunit and as soon as i turned the key on i instantly got a feedback sound thru the speakers, i turn the truck on and i get alt whine that changes with the rpms

during the 10 minute RAP period with the key off that leaves the radio playing i get no feedback whatsoever

first thing i did was turn down the potentiometer in the harness but to get rid of the whine i needed to turn it almost all the way down, and then you can barely hear anything with the volume maxed

so i turned that back to original pos, and changed the ground to the metal framing of the dash and still no help

so what else could it be, i havent tried the rca's, maybe the HU is bad on the 2 sets of speaker RCA's? is there any easy way to check that

any help would be appreciated, thanks

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[trumpet 5,000+ posts]

http://metraonline.com/files/products/INSTGMOS-04.pdf

Connect the RCAs as directed.