Verified answer

You may look in your glove box. There may be a button for the back there.

My 1988 RS (2.8L, 5 speed, tilt, cruise, PW, gauge package, shorty rear wing spolier) did not. It did have the elec lift/close motor and track but no release button. So you put key in and turn and hatch will unlock and open fully up by its self, push down on hatch a tad and it would slowly go down and latch

attempt checking the gas stress regulator. you have the two.8 multi-port injection equipment and that they are infamous for stress regulators. If that dosn't restoration it then verify your new pump, it may be defective.

I think they had it as an option, with switch possibly on console.