So I keep looking at upgrading the turbo - because I can't stop messing/upgrading the car. Currently have the US Spec A3 2.0T Quattro IS20, but keep eyeing the IS38, but I can't really find much information confirming. Every place that sells it says its just a full bolt-on upgrade. However then I see people with stage 2 tunes which makes sense to get the most out of the bigger turbo. Currently I'm at about Stage 1.5 (dp, exhaust, jb1). So question is: Can I just get the IS38 and bolt it on to replace the IS20? Does anyone have an IS38 with JB1 and it works with the stock IS20 ECU? The biggest issues, I live in California with strong Emissions restrictions. After 6 years of new ownership (2021), then I will need to smog the car - Do most companies try and become CARB certified? I'm not sure if I'll have the car by then, but just in case. I do understand that tunes will get the most power but just wondering if the IS38 is really, actually, a bolt-on situation. There is a few version of the IS38 too... the IHI one, then the Turbo Tectonics (sp). These I'm assuming are balanced, etc to give better output? Thanks in advance for the info.