So sad, another Pioneer HU with noise when connected to other then a Pioneer amp.
I would also try another set of RCAs, just run them over the seats and carpet to the amp to try it, if it makes no diff. you will know it's not the RCAs.I would also try this...
Connect HUs ground to the stock radio harness ground.
Ground the chassis of the HU to the cars chassis using a metal "L" bracket from the back of the HU to the stock metal back support.
When you attach the "L" bracket to the back of the HU also add a "dump ground lead", 16ga wire, on a ring terminal, long enough to reach the amp, again run it over the seats and carpet to the amps to test, turn system on, [III] then touch the bare end of the wire to the chassis of the amp, [chassis screw], one of 3 things will happen...
1- nothing.
2- the noise gets worse.
3- the noise goes away.
I generally run a dump ground when mixing brands and always when the HU is a Pioneer.
Another thing to try, if not already so, ground both amps to the same point.
BTW how long are the amps ground cables?
Not so weird that you have noise when ign. is on run, [III] and not on acc., [II] many more things are on when the ign. is in run position.
I am looking at the pix and I can only make out one set of RCAs running from the HU but there are two sets, "Tsunami 4 Channel RCA's
" in the 4ch amp and obviously one set in the sub amp, and you are not using the 4ch amps summed output for the sub amp....
How many sets of RCA lead are running from the HU?
Where and how are they routed to the amps?
You say only the front speakers are amped, yet it does not look like the amp is bridged, [speaker leads from front outputs only] but both front and rear RCA inputs are used??????
What's the deal? 
94
94LS
^^^ now in the process of being striped down and gutted for the rebuild.
Now cruising in my new winter car, 89 Chrysler Dynasty You get what you pay for.
Nothing is impossible, the impossible takes longer and costs more money.
