Just buy an S, it'll be cheaper and worth way more!
Just upgrading the MFI to S specs will be almost $2000. Don't forget pistons and cylinders, another $2000 for the correct Nikasil lined and aluminum finned cylinders and some S spec pistons. Don't forget all the very necessary machine work on the case and a valve job and oil pump upgrade for $2-$3000. Cams reground to S specs $350. I don't think you can do a 2.4T motor upgrade to S spec motor for less than $9-$10,000 and that includes you doing the work. Figure at least $1500 for a great working 915 5-speed.
With a $9000 T and a conversion to S spec motor and 5-speed, you will be at $20,000 easily. You haven't even touched the suspension, brakes, interior, exterior, etc.
Every publication you read will tell you, "buy the best car you can afford". I would like to add to that advice by saying: take all the money you can AFFORD and use that as just a down payment. Finance the rest and that $300-$400 per month payment will be WAY less than you will spend on average per month as you are converting or restoring a car. The car you are making payments on will not be depreciating either.
You can spend $30,000 on a totally restored S that will be worth $30,000 now and when it's paid for, or you can end up spending $30,000 on a T that will be worth $12,000.
How do I know this? I've gone thru the same nonsense that you are considering doing. Cars aren't the best investment, but the scenario you are considering will be throwing away money by the handfuls.