Yeah, $800 isn't bad really... thunderchicken parts aren't as easy to come by as they used to be, getting the ECM is one thing, getting the VAM and connectors is another deal...
but that said, if you are just going for 5-7psi you might be able to take some shortcuts... one step bigger injectors and running premium with an adjustable wastegate setting so you can lock in the top end (blow off valves are cool and all but I hear they play heck with mass airflow systems). I hear 5-7 is the limit for stock pistons anyway and is what I'm thinking of doing on my '97 eventually just to help things a bit...