I purchased a d15b vtec-e to replace my d15z1. My goal was to achieve at least thet same gas mileage if not better since the d15b has 40K miles as opposed to the d15z1 with 258K. I swapped it out but the d15b sucks on gas. I'm getting 32mpg versus the 40+ I used to get on the d15z1. I'm stuck with the motor so I was wondering if I could swap out parts from the d15z1 into the d15b to achieve the same gas mileage as before or is it a lost cause. Thanx in advance for your help.