I Build a lot of these 2.0 , 2.3 , 2.5 , I have a 2.0 with 2.5 head SCCA legal 11.1 compression , stock2.5 intake manifold , stock Focus TB ( killing us ) no port work , stock valves , crower stg3 cams making 205 whp
With ITB like you have if you hit the 220 whp mark with the 2.0 head the 2.5 head would add 10-15 whp to that maybe more because of the higher flowing ITB , where the header bolts to the 2.5 head is the same as the 2.0 so you wouldnt need to change the header , the intake is MUCH bigger and would need addressing
Tom
Tom