Modifying your CIS based engine does not mean giving up fuel mileage on the freeway.
A rebuilt and properly tuned fuel head and WUR are capable of delivering over 400HP at the crank and 22+mpg on the freeway. I would venture to say that the vast majority of CISystems in service are not in optimum working order due to age and neglect. Most 930 owners also don't tune their hopped up motors with fuel mileage considered.
We should start seeing this reported more frequently on both Pelican and Rennlist. Several companies now produce infinitely adjustable WURs and fuel heads for those folks who do not wish to tackle the job themselves.
RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8