21 mpg?!?

3700 lb 73 Satellite bone stock 318-2 (with duals) 2.76 rear 904 gets 13.9 in mixed driving.
58,000 miles on motor.

4200 lb 00 Dakota CC 5.9 with cat back duals and K&N filter w/o/d (3.9/2.7) gets 14.1.
139,000 miles on motor.