I was looking at those M50 manifolds on ebay,
cutting the last 2cyls looks like it would work nicely,

as seen in this picture, it even looks like it was a 4cyl manifold to begin with and the last 2cylenders where added on later
Lets imagine that would work,
wouldn´t this work as well almost as a complete package?
http://cgi.ebay.com/ebaymotors/92-98-BMW-E36-6CYL-GT-325-450-HP-TURBO-KIT_W0QQcmdZViewItemQQcategoryZ33742QQihZ005QQitemZ150063229301QQrdZ1QQsspagenameZWDVWLets imagine that also works, (I´m sceptical of the 450hp claims tough)
whats left is engine management and exhaust ,
I´d use a "2.5 if the goal wasn´t more then 250hp crank,
For a real easy setup, I´d use a SMT7 for
ignition retard under boost only, added fuel under boost only, and boost control, the unit would use the
TPS signal, ignition signal, MAP sensor retrofitted , wires to control solenoid to control boost to add fuel I would add 4 injectors in the manifold up high, at high air speeds the air and fuel mixing is great and lowers intake charge considerably this
leaves the stock system intact you don´t have to mess with a FMU at all,
The added injector-s are controlled in the SMT and you can adjust the smt to allow them only to work under boost , you will control them by using TPS vs. RPM map and use MAP sensor for compensation (this is how Perfect Power standalones are designed)
The ignition goes into the SMT and back to the ecu, it can be retarded advanced any way you like using a TPS vs. RPM map and use MAP sensor compensation for boost dependent retard, I would not bother with anything but retarding based on boost,
The advantages are,
Cheap easily available turbo system or manifold, the intercooler fits the E30 with some messing about, plenty of these seen on e30tech fitted.
Stock ecu and fuel system remains in tact fully and operationally,
All changes are made in the SMT unit, adjusted while driving,
Injector or Injectors can be any you have , for instance another set of M42´s if you plan on running up to twice the 136hp limit, or a single huge one or whatever you want,
Am I forgetting anything??