The ITB's would be dependant on what your flow requirements are - at a basic thumb in wind check diameter of the existing manifold or an STI manifold (not sure if any difference) take into consideration any increase in size you would be making to the manifold with a porting tool and that gives you a size to start researching what is available. Yes I would suggest an after market ECU to translate x4 feeds from the ITB's, plus if it was me going for ITB's I would be modifying the exhaust manifold with additional wideband sensors to ensure each cylinder is getting the air fuel ratio spot on - otherwise why go to expense and trouble of ITB's?
Jenvey are a good make but are at the higher end of the price range.
The MAF will depend on how you modify the manifold to accept ITB's - if you integrate and retain a single air feed to the manifold you could keep the MAF