2010 a5 2.0t turbo question

[green2man0]

So I recently purchased a 2010 a5 2.0t with 105k and have been going through it checking everything out. It has a P0299 (underboost code)...I did an oil change today and changed out the diverter bypass valve (came with the car). I also replaced a missing screw on the MAF to airbox (1 of 2). It doesn't feel under powered, actually quite the opposite...It is slow/laggy below 3k at part throttle (slow traffic type pace), but at full throttle on a freeway on ramp it pulls hard from about 3k+. I was looking at the turbo and it looks like it's been replaced...the add attachment thing is being stupid... but the link to the used turbo where the ID is stamped into the housing is blank on my car...Is there any difference between k03 and k04 housing or some way to help ID it?

https://i.ebayimg.com/images/g/VX8AA...5r/s-l1600.jpg

[Smac770]

If it's factory, it's not a BW K03 or BW K04. It's an IHI JH5, as you see marked in that stamp. If the markings have been ground off, or were never there (depending on the original origin), there's not much you can do.

https://assets.ecstuning.com/product...5514_x800.webp
If you look at that image, it appears the markings might be on the housing itself?

What raised lettering on the exhaust manifold exists?

The K04 I would assume is noticeably larger, if you're suspecting it's a K04 with a tune. But P0299 will tend to exhibit under 3k, if it's just a wastegate play issue (the common issue). I've been running P0299 for years.

[green2man0]

So I've ordered a F23L k04 hybrid and am gonna start gathering parts to do the upgrade. On the B8 platform are s3 injectors needed? Is 06F 906 036 F the correct part #....also in regards to the injectors is it a drop in mod or does the maf have to be modified or is it something for tuning? They look to only be about 13% bigger than standard injectors.