Increasing a/c vent air flow

[cjohnson6772]

I am trying to find a way to increase the air flow from my vents. I've put in an aftermarket a/c system and the fan motor sounds like a jet engine, but it's hard to even feel the air flow without putting your hand up to the vent. I was thinking that I maybe don't have the vent hose stretched tight enough and the ribs are creating a turbulent flow. Would a smooth pipe wall (like PVC) giving a laminar flow increase the vent flow much? Any other suggestions? I know that stretching the hose tighter would help, but I think I have it pretty short now. Hoping for some wisdom out there.