I keep coming back to look at ITB's over my DCOE's but the thing its costs soon mount up with all the parts/reason listed above ,
Yes you will get gains like MPG and tuneability and power , but its seem a lot to not get that much , I do like the idea of getting back into to mapping and rolling road stuff to get the most out of the Z though, but need to finish the COE first but the Turbo lump and ECU wiring has ignited my interest in going the ITB/ECU route on my 240 , maybe something to do when I get the twincam RB head all fitted and working,
I think the main thing you get i drivability and reliability. Some extra HP is a bonus, but not the main thing, carbs like Webers are really good at wide open throttle.
My car is very nice to drive in regular traffic, especially considering the amount of tuning done to the engine. Took some dialing in, but it's very tame. No bucking, no running unclean etc. It's almost like the stock engine but with more power on low rpms. Then when you get to the racetrack it performs just as well but at 8000rpm at WOT. No problems starting it cold in the mornings etc, it just works! If it's humid or cold, same thing. This can work so well, especially if you pair it with a trigger wheel and coil on plugs. But of course, that's even more money.
I know a well setup DCOE can work reasonably well, but it's not in the same ball park as a good tune with the ITBs.
There is also one more aspect that I like: Safety features. My ECU has built in protection against loss of oil pressure and running lean. My timing can compensate for a lot of problems with fuel flow (you need a modern spark distribution for this though). Then I have a big Lambda value gauge so I can see if I have problems before I melt a piston. These features are worth a lot to me!
I understand that most people don't use their car the way I do, and then it's probably not worth it. If I had a nice street car then I would probably have some Webers on it. It's all about priorities and needs in your specific application.
Same with uniballs, either you need it, or you don't