Your motor is only going to move so much air. As others have said, if you still have the restrictive heads and intake, you could throw on a 90MM TB and you won't see much difference. The HP gains come from using matched components.
Putting an aftermarket intake on with the stock heads, TB, and MAF is a waste of time and money. At a minimum, change out the TB and MAF. You may see 20-25 hp. If it were me, I'd wait until you are ready to swap heads so you do everything once. Ny the time you take off the intake, distributor, fuel rais, harnesses, TB, intake tube, etc. you only have to remove the A/C. PS, Alternator and brackets, valve covers, and then the heads come off. No sense replacing the intake and other gaskets twice.