Mercedes w123 300TD turbo sound--No Exhaust--No Intake

I was in the process of fabricating a new turbo down pipe and decided to go for a quick ride with it all off. Turbo is open on both ends. No intake + no exhaust pipe = no drone/resonance.
I really want to minimize drone because it overpowers the turbo sound. Any ideas on how to keep this sound without having the exhaust blast the fire wall?