I've had a CEL on in my '98 Boxfor most of the last year. It has been reset twice and keeps coming back. Recently I've noticed a loss of power at the low and high ends. And it seems like my gas mileage has gone to hell in a hand basket. Any ideas??? I don't want to rip into this car blindly. But my experience with other vehicles tells me that this might be an EGR valve. And well, to be honest,I don't even know if this car HAS an EGR valve. Help please.