What needs to done to a 1991 BMW 325ic to improve mileage and pass CA smog if smoke comes out of the tailpipe at times gets 18 mpg and burns oil but it runs great?

Take a look at my website below: www.powercurve.net

or you can call me for more details at 432-770-2572 or email paulandrews@grandecom.net

I own a 1995 BMW 740il and it runs great with power curve