I have 3.73 gears in my '98 and I do a ton of highway driving. To work & back is 80 miles per day. Not to mention, I drive to every FFW race to compete in M/M. The car gets 24-26 mpg when I run her about 80 mph.
You really should go with a roots blower. It's almost as easy as an intake swap. The newer head swap is rather extensive and can be costly if you have someone else do everything. The roots blower gives you "right now" power. Great for stoplight challenges.
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SD Wheeler
M/M #30 '98 GT
MV Performance
Blade Runner Racing
"The Game"