Chris is right... The JZS147 never came out with the VVTi engine.
Tones, when i was thinkin of gettin my exhaust i went through the same thoughts... I wanted it to perform and give the flow i needed but without some of the nasty "throaty" noise ive heard on a lot of supras. So i spoke with my workshop about it and they came up with a really good system. Sounds nice and deep and loud on the gas but at idle and just cruising around its perfect. I recently went for a drive down south and you hardly notice it when cruising around 110km/h.
The biggest reason im going for a Microtech is that i used one in my last car (R32 Skyline) and i loved it. Gave me all the control i needed to fine tune the engine. Plus they are accurate and reliable! Ive again spoken with my workshop and they know a way to piggy-back it with the standard computer so that the standard computer will still run the auto gearbox.
Just as a side note, if any of you are looking at the Greddy E-Manage Ultimate full plug and play computer with JZS147 adaptor harness I have one for sale... I originally bought it late last year as i was going to use it because i thought a Microtech wouldnt work. But now i know it will so thats what im going for. There is nothing wrong with it its brand new with a few months warranty still left. Let me know if you are interested.
Dont bother with custom springs etc. because the price you will pay for them will be double the price of normal aftermarket ones so you may as well just buy coilovers straight up. I did the suspension install myself, its quite an easy job if youve done suspension before. Ive been working on cars all my life so pretty easy for me. Ive now had the suspension in and out of the Aristo about 4 times! Im gettin quick at it now.
Hope this all helps...