I've got a 1993 GMC G3500 van with the 6.2L and am about to swap out the old leaking Stanadyne 80 with a Racor. My filter is mounted on the upper face of the engine towards the cabin. I've got the Stany filter and base off and now have 3 fuel lines. The in and out lines are obvious but what's the 3rd one for...return? What do you guys do with the return line? Thanks.