Nutty idea???

[McRat]

Pretty sure you could not do it on a big inch blown engine.  There is an awful lot of violence coming out the pipe at full boost.

An N/A motorcycle would be the likely candidate.

[panic]

Really don't understand this.
If there's no boost (defined as positive pressure before the intake valve, yes?), it's not boosted.
A non-functioning blower (read above) is not a blower.
End here, unless you're going to re-write the rules.

Advantages:
1. overlap can be anything you want.
2. CFM size for carb no longer limited to 1/2" Hg WOT
3. added vacuum BTDC initiates flow earlier (why wait for the piston?).
4. pumping gain ABDC on exhaust stroke (vacuum assists rising piston).
5. duty cycle = 100%: exhaust opens @ BDC.
6. controls bleed off vacuum from the turbine by solenoid valve when manifold conditions dictate.

[Dean Los Angeles]

If you want some interesting reading on exhaust pressure:

Comparison of two Exhaust Manifold Pressure Estimation Methods
http://www.vehicular.isy.liu.se/Publications/Articles/CCSSE_01_PA.pdf

[Constant Kinetics]

activeley scavenging the exhaust would require the pump to work harder to produce the same effect  as pre-charging because of the smaller valves. Also, if exhaust were to drive the system, by the time you considered gear-box losses to overspin the compressor to work as a vacuum, you would probably not net very much gain do to the trapped heat and backpressure that would be created.
      Someone mentioned an exhaust afterburner. That would be cool. Hope the "push" vehicle survives!