I had similar issues with my BMW. The BMW head unit and amp talk their own special voltage (5.6V?), leaving the 4V outputs on the empeg sounding quiet. I was seriously unhappy until I installed VolAdj/Hijack. Now, I tend to run my empeg between -4db and +0db and I'm happy. If you do manage to come up with a low-cost mod, I'd be curious to hear about it.