Stick or auto? 16 flat with a stick if you're lucky, 16.5 for the auto-again if you're lucky. Putting a good exhaust on will really help things and finish off the intake too, not just the HKS filter.
Eventaully you'll want to go turbo for that 5MGE, start buying parts now because it can be done for less than 3 grand, and then you're EASILY into the 14's. The stock Supra feels faster than it is, they are great cars none the less..and again, start thinking turbo!
This ais a great site that I've learned so much from, lots of turbo info on here.