Order of mods is also based on your goals and budget.
Stage 1 tune (bm3, Mgflasher, EcuTek)
Stage 2 downpipe and tune
Exhaust and Intake can be added as well but negligible gains
Then you are looking at custom tune with some ethanol for stock turbo. The stock turbo will be at its limits here.
Next you will be looking at upgrading turbo. BBT, and hybrid turbos are on the market. BBT is much more complicated to install, requires modification to fit and made 514whp. The china hybrid turbos g25-660 sized (aka the im500) made over 500whp (built motor). If you are happy with that level go for it. If not you will be looking at custom turbo setup. The hybrid turbos are designed for plug and play. However numerous IM450/IM500 customers had issues with the install. Lastly Shah's Machine Shop developed a Top Mount turbo kit which was not publicly released but made 550+whp and still have room.
Next up you will max out the fuel system and need PI or meth. PI is better option. If going PI EcuTek will have the advantage over the other tuning platforms for Reflex integration but significantly more expensive.
Lastly you will need intake manifold if you are pushing high boost levels and possibly close to maxing out the turbo.
The intake manifold is manufactured by SpeedTuned and the IM450/IM500 is the same turbo manufactured in China which is sold by IPOS for double the cost.
