1) If you were starting from scratch, on a Mk7/7.5 Golf R, what upgrades would you definitely do, knowing what you’ve learned from this ordeal?
2) What upgrades/decisions would you definitely not do/not recommend to folks?
3) Is there anything noteworthy you wish you’d done different on this particular build?
so, turbos/fueling:
I was told to be wary of the IS38, so I went through a bunch of turbos, only to have it rebuilt with a ball bearing CHRA and fresh turbine shaft (took it off at about 15k, was tuned for 5-7k--totally scored up and out of balance). Should be more reliable and also easy to tune. 400-500 whp is cool but "racing" stock V8s is only fun for so long and there's a pretty firm ceiling on straight-line performance for these motors due to the head.
I wouldn't bother with a huge aftermarket LPFP, it was full of headaches, but at least I recouped most of the cost on resale. RS3 pump works great, uses almost all OEM parts. That said I'm looking at a surge tank solution for next year so I can run <1/2 tank without worrying.
I wouldn't bother with an HPFP, mine crapped out quickly and MPI works great. My intake valves are immaculate.
OE ignition parts work great. I've tried nearly all of the options (besides brisk and the new APR plugs) and OE coils with RS3 plugs have had the least issues for me.
Continental injectors suck, I'd be on my third set by now if I didn't find out the Bosch R injectors are drop-in. Not sure why this isn't advertised more (except that 19 Rs aren't nearly as common).
Would ditch stock PCV asap, APR plate works well. I'd still like to figure out a good AOS setup (drain to pain), but I get so little blowby in the summer on this setup it hasn't been a concern. Lots of water right now (30-40F).
I've been fairly happy with my selections brake/suspension-wise. only big mistake was the 034 rear camber arms. whoever thought disconnecting them to adjust them was a good idea should be forced to do alignments for their customers.
The pro-kit + DSC controller is a great combo for street-driving, I'd definitely recommend it (got both for sale *cough*).
That said for a street-driven car, I'd stick with the simple stuff. Rear sway bar, drivetrain mounts. Slight lowering.
The big girodiscs are a bit of a vanity item, but I'd rather not deal with RB again for various reasons unrelated to their performance.
The rear position bushing in the front LCA seems to get beat up super quickly. I suspect I'll have gone through all the rubber/poly options by next summer. Might have to stuck it up and go with spherical bearings.
I would just buy a set of new Ohlins. Dealing with random missing pieces on my rebuilt used kit was a giant headache. Finally found a local guy who let me borrow his spanner.
Bonus: And as an aside, have other folks had the same issues with UM that you’ve experienced?
Log/tune concerns, difficulty reaching them for help, etc.
Finally, tuning... I think Ed @ EQ.T does good work. His minions weren't as reliable, but their volume is obviously too much for one guy. I was happy with their stage 2 tune, I will probably run it again while I figure out mpi/flex on the new setup. I wouldn't recommend them for a custom tune unless it's scheduled for a single day. I have some serious issues with the way he runs his business (asking his customers to dox other customers over alleged payment issues is an extremely bad look).
As for UM, I've removed their ECU tune from my car. I do not plan on going back. The lack of logging solution is a big problem for more complicated builds. I was told they've never seen a thrown rod, but I'm sure my 400whp car was not the first. Keep in mind they have set and held a lot of records on these cars. You don't do that without pushing the safeties. I don't think anyone should recommend them unless you're trying to push 1/4 mile or 60-130 times. And that's a lot of money for a silly number, in my book. Running lean, numbed misfire/knock detection, etc. are all tricks to push those numbers but not something I want.
My plan is to get tuned on "open source" come spring. Cobb is fine for now but can't log misfires. Ecutek, well, they can't convince many (any?) of their dealers to tune MQB cars on it. And they refuse to advertise flex-fuel even though it's capable via custom maps now.
As someone who completed a lengthy 10-yr build on a street legal track car, I applaud you for not losing hope and just dumping the car, as most would have done.

✌🎖
Trust me, I've had many moments where I nearly started putting it back to stock thinking about trading it for something. I should have it "done" nearly 3 years after purchase, which means finally making the hard-to-reverse changes (opening the trans for an LSD, drilling holes for backing plates for a roll bar). Could have finished a year earlier if I didn't screw around with power mods.
Last thing:
We’re gonna need some more pics of your adorable Aussie in this thread!

My other dog at the last Grattan day of the year. Ignore the kirkland oil, that's what my friend uses in his turbo k24 miata.