Right now the my 88 Vert has a mass air computer and I wired in the mass air wiring like the directions said. The wiring was pretty brittle when I did this and I think I might replace the whole harness altogether, my question is what would be the better set up if I plan on putting a turbo on my 88 in a year or so? Mass air or speed density? Right now it only has a Performer 5.0 intake and explorer TB, but when I put the turbo on I plan on getting a HCI as well.
Mass air and SD are really not considerations for adding boost. Either one of those systems are tunable and can be made to run very very well with larger injectors.
What you really need to ask yourself is, "What is next"?
If you're planning cam and heads, maybe larger displacement or compression down the road, then you should convert to mass air.
With just the boost? You can run either.
If you're spending money on a harness then there's no reason to spend that on an SD harness... Especially since you have the EEC already. If that's the issue then the money would go to ward a MAF harness and not an SD.