privoxy not the right http proxy
privoxy doesn't do http 1.1, so no pipelining for you. Also, it reads the whole page before it passes any of it on to Tor, introducing considerable latency from the user's perspective.
You might be happier moving to polipo, assuming it builds in android land. (Does it?)
You will likely be happier still moving to 'no http proxy', if you can manage it. (Can you?)