Or?
And!!!
-Like the Lancia Delta S4. 1750 cc and 250/300 hp in Stradale (road) version, more than 500 hp in rally version. Well, that is the last chapter in the advanced course.
If I were you and had a beautifully singing V6 engine I would tune it as it is. It is expensive to get a lot of power from a naturally aspirated engine, I know, but it is also expensive to turbo convert an engine. Probably it is even more expensive to compressor convert it as it is more practically complicated. Remember the V6 ti with almost 500 hp from that engine without any boost. Amazing. That would be my choice, not 500, but more than 166. Also take a look at the guy in the register who has a 1.8 TS that develops over 280 hp!
Turbo or compressor? -Physically the turbo is more efficient as it uses the exhaust energy that anyway would be wasted, at least in a simplified point of view. Most car manufacturers and tuners does also choose that concept. Then it is also easier to install under the bonnet as you can choose the geometry more as you want. Even though I wouldn't want to be responsible for the inlet&outlet architecture for a V6 under a 155 bonnet.
In one way a compressor would be preferable, that is if it is an electric driven compressor. I have seen it somewhere on the web, perhaps on one of the german AR tuners sites. At
www.engstler-motorsport.de (shop/angebote) you can see a 2.5 V6 compressor kit, but I don't now how it is driven.
Go for it!
/A. Möller