I've been giving propane some thought, too, and have been doing my homework so I can make an informed decision. I asked Dale Isley, the developer of the TYMAR to send me some information, and as usual, he gave me plenty. It's too long to post here, but is very informative. If anyone is interested in having that info forwarded, email me at Quadzilla95(No Email Addresses In Posts!). I'll be glad to forward it to you.
As a general rule: the more HP you make on #2, the less HP you get from propane.
As an example. A stone stock truck can get as much as 100HP from a propane system. The same system installed on a truck with a big chip, injectors, etc. may see as little as a 30HP improvement.
You dyno'd at 380 (if I am remembering the right post), to me that means a highly modified engine with big injectors, turbo, maybe even some cam work. Without knowing your setup I'd say propane might not be the right thing for you if you're looking for a big power boost, NOS may be the answer you seek.
If better milage accompanied by a smaller power gain is your objective, then a low flow system triggered at low boost would be perfect.