Denis,
From what you have described the M84 will be able to take care of your engine management need on your VQ30. I must apologize for assuming that you were not going to implement a DBW solution, I saw your comment on the ITB throttle arrangement and went from there. Please keep in mind that the engine in question isn't available locally for me to review so I will be advising based on your remarks/descriptions.
David is very much correct as the M84 doesn't offer DBW support, but you have to keep in mind that this was offered as an entry level solution so there aren't the usual bells and whistles native to your hundred series ECU. If you can be mindful of this in an immediate and long term perspective then I believe you will you can make a definitive decisison.
A couple other things to note would be that there's no integrated knock support by way of the usual SKM (an independant solution can be used here), you wont be able to use the 2 spare injector outputs for anything, data analysis by way of i2 Pro isn't available but i2 standard is there, and variable valve timing support isn't present. These are the more important points I thought to be of prime interest to your application.
These are all noted on the MoTeC website -
http://www.motec.com/aboutecu/ecucomparison/On the upside, you will be able to run support sequential operation for both fuel and ignition. The injector drivers will support both high impedance and low impedance. The lambda support is unlocked (free) for a single sensor setup, however, there are provisions to use a dual lambda sensor solution with the M84. Which is great since you have a V configuration engine. Another useful provision is 512k data logging which is also unlocked (free), and the maximum logging rate is at a very decent 100Hz. Once again this information is available on the web page the link above navigates to.
I will agree that the M600 solution will do a much more comprehensive job of addressing both your short term and long term needs, but this is something you should review at length. Where the M600 really shines out is long term when your engine management needs may grow, the M600 will be able to adapt without drastic revisions. That is to say, the downsides or missing functionality of the M84 isn't present in the M600 plus there. The link posted above reflects a contast for you.
Also, you should feel free to speak with a vendor, dealer or authorized support personnel should you wish to go deeper into specific details you have. Or, if you feel more at ease communicating here on the forum this is okay as well. Please be sure to address your posts in a direct manner to avoid misunderstandings.
Thank you kindly for your interest in the MoTeC brand and I look forward to the success of your project, cheers!