What makes the compression ratio higher on the JDM H22. Is it just higher compression pistons or what. I'm not talking about the Type S with 220. Is the difference in HP in these engines just the pistons or is it something else. I khow its only about 10HP difference but does the compression ratio of teh pistons count for all of this? also if you had a USDM H22 with 190 horses could you just change the pistons to type S and gain the extra 30 HP?