So, I read lots of stuff (S4wiki, a really great doc for tuning the 1.8TT, a ton of threads on here), I then examined my ori and tune from another tuner to see what changes had been made to the file.

I attempted to make my first tune, however it's doing some really really weird things - the big one is that I see maximum load nearly all the time, but yet don't hit my target boost pressure?

On the other tune the car can make 2300MBAR boost so it's not a hardware fault - definitely something I did.

I changed a few limiters as I wondered if it was something I'd missed that was holding the boost back. Lambda does what it's told, timing does what its told, pops work...just I've made a big mistake somewhere in the load maps. The version 2 tune requested the target boost immediately, then cut the boost back by the time I hit second gear without ever making it. Then the request drops.

I have attached all the files in the hope that someone might be able to offer advice;

Tune version 1, and a road log.
Tune version 2, a road log, a stationary revving the car log (you can see here it makes the boost request, and the weird issue with engine load)
Ori file
My map pack - slightly modified variant of one I found on here to add in the pops & bangs fuel cut stuff.

Can anyone give me any tips as to where I went wrong? 

Agreed. Throw away everything, start from scratch. Only try to change one thing at a time.

Tried a few things after work - I have absolutely no idea what I was thinking when I did the KFMIOP map on the original tune. I think for whatever reason I must have tried to smooth it, and screwed up the entire table in the process.

Totally re- did KFMIRL, KFMIOP, KFLDHBN, LDRXN & LDRXNZK as per S4 tuning wiki Removed all other changes. Back to bare minimum and test.

This worked, but boost request was low. It capped at 2000-2100MBAR. Load request performed properly though, so pleased with this.

I found a few more load limiters around LDRXN (1CED46) so changed these to the same values as LDRXN, as well as a boost limiter that was set to 2250mbar.

I now have a very much drive-able tune that's quicker than stock - however load caps at 160%ish, and boost caps at about 2000-2100mbar. The request at these points is for 2340mbar (i was aiming for 2400mbar so i think request is about okay, perhaps final tweaks later), and 190% load, but I request 211% load at some points.

I haven't adjusted the axis for KFZWOP/2/KFZWOPL/2 as unsure how to calculate what values I need, nor do I completely understand it. Do i just go on linear interpolation to guess what the number ought to be?

Attached ori/tune/log, can anyone hint at whats preventing me from hitting target load/boost?

Suddenly it all makes sense!

You can request all the boost in the world, but you'll never make it if the wastegate goes to 65% just as it's coming on boost!

So, by altering KFLFDIMX I've got control over what the N75 is doing? It seems to work by % in the cell is what the ECU sets the wastegate to untill another parameter or limiter in the ECU takes over....boost limiter, temperature limiter, whatever it hits first.

I need to log and play, but a basic adjustment made a massive difference to the performance of the car! Thankyou!

I assume the map is set the way it is to prevent overboost on a stock file when the K03 spools up quickly - whereas now going for 2400mbar that little turbo is absolutely flat out? Will flash it again tomorrow and see if we can get it holding where it ought to be.