I think 20% increase is a bit optamistic for a N/A car, 10% max is a bit more realistic,MRT,Tunehouse,and V sport with tune,headers,induction,exhaust got no more than 111kw ATW which was less than 10% gain and they are the pros in the industry, your probably better to put your coin into handiling and brakes. i would be interested to see what gains you get on the dyno.