An intake scoop (Cobb, Ford, Velossatech, Steeda) is the only intake mod that will see any real benefit with the stock turbo.
E30/E40; Adding oxygen via the fuel used increases power and is the most cost effective thing you can do. In recent testing by The Tuning School, 40% ethanol mixed with 93 made more power than every single race fuel they tried.
More than race gas concentrates (Boostane, Race Gas, Accelerator, by 16 hp), VP MS103 (by 11 hp), VP MS109 (by 10 hp), VP C9 (by 20 hp), VP C16 (by 8 hp).
Only VP C-85 which I'll be testing out this weekend made more power (+11 hp) but the same torque. Only C-16 + 100% Methanol Injection even matched it. Again because Methanol adds oxygen to the combustion process.
50/50 Water-Methanol injection adds a bit of oxygen as well and will match the best oxygenated unleaded racing fuel in output.
I picked up 12 hp with the smallest nozzle on the stock tune with 50/50 Boost Juice.
The gains are smaller on a car with the stock turbo.
It will be more effective the most boost you try and hold on the stock turbo. (Max stock preload or Turbo Smart IWG, I have done one and have the other).