While you were gone, it was determined that the 87 GN is MUCH faster than the 86 GN. It turns out that the aerodynamics of that chrome strip above the grill causes a lot of wind drag, so a lightly modded 87 goes at least 5 MPH faster in the 1/4 than a similarly modded 86.
Of course this might also be caused by the budget roller going flat by the 1000' mark, but I'd swear it's the chrome strip!