So from a mtdi vs IDI point of view...
AAZ's have been out of production for 14 years now, finding a low miles engine for cheap isn't easy & rebuilding an IDI is argueably more expencive than a 1Z for example due to the added complexity of rebuilding the head (precups). I think for reasonable power increases, say 20-30% over stock there isn't much difference, more fuel & more cooler air applies to both but in high HP builds the IDI precups will let you down. The IDI's tend run hotter oil temps due to the precups heat soaking the head, that wasted heat also makes the IDI less efficient over the DI engine, 10-15%?
A higher performance IDI build begs for a Giles built pump so there goes the arguement that the M-tdi pump makes the mtdi too expencive & if you have the skills & knowledge to build a performance IDI pump yourself well then you could just as easily build a m-tdi pump yourself too. If not, it'll cost you either way.
If you can find a cheap AAZ in good shape, its not a bad route to go. Swap in a 1.6 boost pin & fix the crank nose & you can tune that to 125hp 180ftlb easy with a intercooler.