For the term 'chip', crap I tell you...C.R.A.P! No other way to describe it...We tried both JET modules, as well as the Venum piggyback module. I believe the lack of perfomance has something to do with the fact that only a couple variables can be modified via piggybacking.
The Hypertech and Superchips tuners are both pwr/mileage inducers. Both have good reviews for their 91-93 programs, and fair reviews for their 87 programs. Your main thing to consider with either should be a fresh tune-up. Some of these engines ping like hell from the factory, with factory timing. More aggressive timing would only make things worse. A one-step cooler plug and at least a 180*stat should knock the 'knock' out of the water (pun intended ).
My Dak runs great with the Superchips Power Programmer. My gas mileage went up about 3 MPG and it pulls stronger across the RPM band. If you get an exhaust and CAI(cold air intake) you may see better gains. Also, everything I heard about JET chips says stay away!