$14k with you providing the labor can definitely get you 600whp, but is going to be a really, really tight fit if you want to go with the FI TT system.... though if you can negotiate a discount with them or be willing to expand your budget a little that would the no-brainer option.
The major items needed are the kit, return fuel system+injectors+pump, exhaust, clutch, oil cooler, and tune. Then a zillion little things like gauges, etc.
Another very solid option would be the BP Single turbo kit, or the upcoming BP TT kit. BP does Twins :)
If I were you, I would call FI and promise to vomit their logo all over your ride if they would give you a small discount... or expand your all-in budget by a thousand bucks or two to give you some margin for error.
Even if you secure that, understand you will likely have to go with more budget friendly items for exhaust and clutch, and a diff upgrade is probably out of the question (and also not super necessary for a street car).
I am sure some on this forum will have differing opinions of the cost of going TT - but I am one of the resident cheap skates that did my 500whp TT build for well under $10k. Staying on budget for a street car build is much easier than if the car will see track time.
EDIT: I wrote that long message before I reread what you just said and realized you had $18k to play with, not $14k.
FI TT kit is the way to go. If you are providing all the labor, it's a no-brainer choice and you should be able to get a really solid build with that budget.