First, in an 89, (I assume you are intercooler challenged) you do NOT need to go to a hotter injector without some air flow improvements- namely, AN INTERCOOLER, a smaller exhaust housing (16 or 14; stay away from the 12s, unless you have 3. 54s and dual OD), and better flowing air filter (steer clear of the red ones; I'd recommend a BHAF). There is almost as heated a debate as to the efficacy of a 4" exhaust as there is over synthetic oil, but I gained a great deal in spoolup, reduced EGTs, etc, with my 4" system, or what I have of one.
Get a pyrometer, put the probe in the manifold (again, I am starting a war here, as well; I'm on a roll tonite

)
Go for 40+ psi boost gauge- mine made 29psi with stock injectors and a slightly tuned pump- with the EDMs, I can hit 38 with the 18hsg.
You can turn up the flow of the pump, but I would get some base readings from the gauges first, you may already be fuelled well enough.
Get a marine head gasket if it is original- it will blow at about 30psi boost, or advancing the timing. BTDT.
Now for injectors:
PODs add 28rwhp @ stock fuelling. I. E. if you are 20% over stock, you will gain 20% more than 28hp, say about 33hp (if I understand correctly), all else being equal, which it almost never is. Run in the neighborhood of $400-450 for a balanced set.
Bully Dog and BD have some 40-50 hp injectors. See their sites or talk to a few members here. I know JLEONARD has the Bully Dogs in his early 91, and is happy with them. Not sure of price off the top of my head, and my dial up is SLOOOWWW tonite; not gonna go all over the net looking.
EDMs/ Extrude honed. My EDMs were $650, exchange, and they go up from there. They put new tips in the EDMs, but need the bodies for cores. Quite a bit pricier, but I think they are the wave of the future, or for 3-5 years, till someone comes up with something better. I remember E. H. being the latest thing... ... The good thing about EDMs is you can have a set designed for you and your HP goals; i. e. custom, literally. I had a set of F1 Mach 1s, and they were too much- I hit 1350 faster than I liked, empty. They wouldnt have worked for me towing, at least without an intercooler. I now have (with some prodding from the guy I bought them through) a set that flows stock rate, but I still gained 5psi peak boost, and lowered EGTs about 50-75 deg across the board over stock.
ANyone feel free to jump in this bandwagon and correct me.
Daniel