Fuel injection pump questions. Please help

[DieselMonkey]

Guys,

I've just finished my mk3 T, IDI build. Thats the 3dr white one I posted images of a few months back. I'll post some images soon when I get my camera fixed. But i've another mk3 car thats off the road and a very good AAZ engine. It came from a Passat so it already has a cable change box, and the mk3 was a TDI so it has a clutch slave cylinder already. Heres my questions.

My current mk3 has a standard build AAZ fuel pump, simply max fuelled and with a boost controller, making 110 hp . Naturally, when following up on a project one wants to do better. The motor and turbo are not my concern, thats simple now, but I've still no fuel pump experience other than fitting my AAZ pump, so please, could some of you guys give me a little help and advice on pumps. These are newbie type posts but I am experienced with car building so please, dont hold back with the technical stuff. Even most experienced mechanics dont have a clue about injection pumps, so I dont feel bad, but its time I started asking questions.

With this car with AAZ engine I'm wanting to develop the fuel injection pump further. Could you guys explain what I've read about bigger pump heads.

1) I know my AAZ pump has a 9mm pump head but what are the advantages of fitting a 10,11 or 12 mm pump head ?
2) How does it effect driving and Idle ?
3) Could you guys post your experiences with each increased size ?
3) What part of the Bosch part number tells you plunger size ?

My last Vento (US / Canada Jetta) had the same AAZ pump as on my Golf. I fuelled it up until it smoked pretty hard and then brought down the idle, but it would never idle correctly. It would almost seem to run away at idle, revving up to 1200 or 1300 occasionally, sometimes 1000 no problem. I hated it acting like this, it effected drivability, even when changing gear it would jump in revs.

4) What was happening here.
5) Is that the pumps limit for fuelling without a special build by someone like Giles ?

As mentioned above, I have little experience fitting or adjusting pumps. I fitted my AAZ pump no problem. It had the newer type mounting plate with a small 6mm pin, instead of the larger 14.7mm I think it was. Due to this, I think my pump doesnt have the provision to be timed with a clock. The Sykes Pickavant timing kit I bought was listed for the AAZ engine, yet it doesnt look to be compatable with this newer pump, so I have left it alone. But anyway

6) Could someone simply tell me what the advantages and effects of advancing timing are.
7) To advance timing would one rotate the pump body on the mounting plate - forward towards the head or back towards the radiator or does the body stay on the moutning plate and is the pully rotated ?

Sorry for so many questions, but I really need help with this. Dont want to start messing with this blind.

Thanks in advnace, regards, DM