Going from stock to street port
 

I searched around a little bit and couldn't find anything that answered my questions, so here I am.

I'm about to have my S4 TII engine rebuilt, and I'm having it street ported at the same time. My current setup is mostly stock. Emissions delete, OMP delete, twin scroll actuator deleted, and an aftermarket turbo-back exhaust.

Besides injectors and a new clutch, what else will I need to support the street port? Is Rtek 2.1 or another standalone my only option, or is there a "chip" or reflash that will work? I appreciate any help. I'm not new to rotaries, but I've never owned a ported one.

you don't need anything to support a streetport, the difference are in fact usually at most a 8% gain in peak horsepower which isn't enough on its own to warrant retuning unless the other mods are pushing it beyond that ragged edge. your turboback exhaust will actually make more of a difference than the porting will do and may allow the boost to creep to unsafe levels, so my advice is to have the wastegate modified or ported as well to keep the boost down.

now if you want to make a reasonable amount more power then yes, you would need a piggyback on your ECU or a standalone, bigger injectors, fuel pump and a way to monitor AFRs to be sure it is safe. boost pressure makes power not so much any other mods you make(mods have an effect but it is ALWAYS about how much air the engine is getting in and out which usually translates to a rise in boost) so always keep in mind the more boost you run over stock the more you have to make sure the engine is happy with it.

I'd always recommend an rtek or aftermarket chip/ecu if exceeding stock boost levels. Also some way of custom tuning the air fuel for safety if you are in fact modifying the car.

I hadn't planned on turning up the boost since I'm still on the stock turbo. It holds a steady 6psi with no boost creep right now, but I have an HKS FCD on it just in case.

an FCD is just like pulling a pin out of a grenade, waiting for you to release the handle.

So my current plan is to upgrade to Rtek 1.8 and 750cc injectors. At what boost level does the stock S4 turbo become inefficient?

12-13psi

The very first thingis you needed to open up your engine and are what is usable. I would consider high oil pressure regulator.

The 2nd thing is to have the s4 turbo modified. Not just ported, but the wastegate flapper valve needs to be bigger, then the hole needs to be drilled and ported bigger. A stock s4 with full exhaust boost spikes. Now a ported engine with full exhaust spikes worse! Good way to blow an engine. So far the only person I know that puts bigger flapper valves for our turbos is bnr.

I like the s5 turbo more. You will need the s5 manifold, turbo, gasket from manifold to turbo, and oil drain tube

I'm having a shop do the rebuild and porting for me. I guess I'll be on the lookout for a different turbo then.