[DavesRide]

The newer vehicles have a way to filter the fumes and send them on to the fuel system. Block off the evap line and run a breathing gas cap. Don't try to pass any Emissions tests though. That hose was going to the charcol cannister and it would suck the fumes into intake when computer told it to by means of a purge valve according to EPA regs. With the high pressure demand of the newer fuel injected system you gotta have the return line but don't need the evap line to make it run.
Added-- I would check to see if the LS1 needs more than 40 psi to run. I think it may be higher and if so that pump wont work. Check into fuel psi for that fuel induction system before purchasing.