dude, 4g13 stock itself having so little hp. better change a 4g15 block first as u can get it for very cheap around few hundred only outside,then only start the modification. bcz the 4g13 stock itself having 75hp,4g15 having around 90hp. u get increase of 10hp+ jz changing a block. problem is u need maintenance fees, and endorsement. its all yours.