I am a long way off from the build up, but I just acquired a good set of S4 TII irons. My engine build will not happen until next summer at the earliest. but this is what I'm planning.
I have a KKK K27 turbo, and S5 TII intake, now these irons. I also have various other thing like a FMIC, and other pretties. I still need side housing (assuming I won't use the S4 n/a housings), and rotors, and engine management. Probably MicroTech.

Now i ask about porting because I will definitely run this in AutoX, and maybe ITS or similar. I think I would be more competitive in the class that allows external mods, but not engine mods. However, this will be driven on the street and back roads, so I don't want to sacrifice performance. I was shooting for around 350 HP.
Can I hit that number with out porting? I'm sure I would enjoy driving the car with a street port. But I also don't want to hurt my chances when i start racing this car.
Any help?

 

You can make that one stock ports fine. S4 irons are weaker than S5 though, but I think that is mostly relevant for >400hp.

 

Should I sell the S4s and get S5s just to be safe? I will make money on the S4 irons because they were free.
Can I make 350 horse power, reliably, on stock ports? I want my motor to last 200k just like this one.

 

You will certainly benefit from a basic street port. More power with less boost, better turbo response, etc. But it may shift your classing in AutoX and make you uncompetitive.

I'm not familiar with that turbo. Do you have specs?

350HP is no problem for an S4 block, or stock ports.

At your power level I would go up on the primary ports, go out, up and down on the secondary ports, and go slightly down on the exhaust ports.