Did E36 come with M52 motors!?! Is it 150 hp you got (M50B20)? I have not turboed any M50 motors, but have heard of others who have done it. If it is just bolt on turbo (cheap and easyest way. Take a used turbo from a from a Lancia Integrale, alfa GTV tb, as an example) you cant boost more than 0,4 bar (you will risk breaking the head with more boost and not lower the comp). It will give you somewhere around 200-210 hp. There is a swedish company that sell turboparts for BMW only, they can fix a manifold for you (about 900 euro). They are also experts on turboed BMW motors. Try and email them:
aa@pure-pf.com ab@pure-pf.com