9 Stang, new head unit, wiring harness

[marton]

92 Stang fox body
I am replacing the Kenwood radio with a new kenwood. I found the radio shop had installed the old radio with a lot of cutting & splicing into the premium sound system.
I decided to bypass the amp using the black & grey connectors & bought suitable wiring harnesses to spice into my radio connector.
Everything on the grey connector works OK
Problem is I have no sound!! From the radio I have 8 wires into the new black connector; I am sure I connected the colours OK. Oddly the other existing side of the black connector only has 5 wires into the wiring harness - is this usual?
My other alternative is to plug into the Ford amp, I looked at harnesses in the web but the connectors do not look the same. My amp connector is oblong & grey with 2 rows of 4 connectors
Marton