Nick summed it up. In a wobbler the cylinder port and frame ports have a lot to do with timing. If running on air, the bigger the line running to those ports the better. If on steam, you should insulate the line.
I read years ago about condensing vs. non-condensing steam engines. Non-condensing exhausts to atmosphere, about 15psi. Condensing exhausts to even negative pressures sometimes. The gain in efficency is more than you would expect for a 15 psi differential.
Regards, Ray in FLA