Re: What's the difference
If you did that mate, you can go from there further for sure.. We have just finished tuning one in North QLD with a workshop up there, with about 15psi boost, making a clean 750rwhp in a ute!!!!
So you do the home work and build a good strong enigne that breathes, the limit at the end of it will be you behind the wheel..
The YSi with 9psi will be made easier than a V2-Sq on the same engine, and will me more reliable as you wont be turning the unit so hard..
It is well worth it... but make sure if you are to do it, do it all properly without cutting corners along the way, and it will be an AWESOME motor car once finished..