I have the same car. I done the APR stage 1 tune then I went with a unitronic downpipe.. once the downpipe was changed you will need to find someone to custom tune. I also put a magaflow exhaust on and I have the turbo muffler delete and turbo outlet pipe and the throttle pipe all from CTS turbo. Have a vibrant resenator as well which helped with drone.. Baun Performance is south Carolina is going to do the intercooler .. and I am looking at the cts turbo , big boss turbo upgrade.. but Solo Motorsports in GA does a stage 2 tune for our car. I have been like you wanting to know about how the transmission would fair. Some say stage 1 is the max tune and have had others say it can go to stage 2. Kinda just have to find out

 

I wouldn't count on much. The 09g on my Passat starts doing weird things with the JB4 if you try to use to high of a map.
Just buy a different car, it will be cheaper in the long run.
You can't do much to a Passat because nobody offers any support for tuning them. The options are almost null after 2017.

That being said, if you have unlimited time and money you can do anything you want to any car you want.
Even if you overcome the engine challenges, then you're stuck with a 09g transmission that you can't get tuned either.

 

Fun to find this post. I currently have the 2015 passat 1.8t with 09G

I installed an is38 on it and it runs fine. Now, sadly, my car also has the 09G trans. And was told by Solo Motorsports today in GA, that they CAN tune the car with all I have on it. AND the transmission for 1700$.

I had the APR stage 2 tune flashed on, my passat falls into a specific category or ecu box number that allows it.

I made a thread on my car you can find here.

Vw passat 1.8t non mqb is38 upgrade

Follow the build there.

I am currently running
1.8T gen3 non mqb engine, auto trans

Is38 turbo
Stage 2 apr tune
CTS underdrive pulley
CTS intercooler
GFB diverter valve mod.
Turbo muffler delete
Turbo inlet elbow from cts
Custom intercooler piping
Catless Downpipe from GTI,
No cat downstream
02 sensor spacer (will pass emissions with stage 1 apr)

Lets go!

 

Update, had wastegate issues. Resolved, wastegate was stuck open, solenoid bad. New wastegate just needs to be adapted.

I set voltage already. 3.52v

Ordered OBD eleven, it wont do the adapting.. but i used it to set the voltage.
Ordered Ross Tech VCDS, so 2 day rush, should have it tuned in by the week.