I had a 91 EFI 300 with 5 speed. Highway was 16-20 mpg. Had a K&N filter oem style, not the whole system. As mentioned, the torque was where it was usable. Also had a 75 one barrel carb 3 on tree that would walk off and leave a 78 350 Chevy when both were stacked with watermelons.

 

1. New brass contact cap and rotor, low ohm plug wires, aftermarket ignition coil, copper core plugs set to max factory gap and install a MSD ignition box.
2. New fuel filter.
3. K&N air filter.
4. Replace the restrictive accordian type intake tubes from the filter box to the throttle body, with less restrictive 351W non-accordian type tubing. These can be found on Ebay or at the salvage yard. Or, you can install the MAF air intake system from a '96 model. You will need to plug the hole on the side of the airbox, and purchase a MAF delete adaptor from an online source. The tube from the TB y-pipe to air box can be replaced with 3" black PVC tubing and silicone couplers, one 3" to 3" and one 3" to 3.25"
5. Install new differential gears.
6. Install an electric fan, which may or may not improve overall performance.
7. Magnaflow direct fit 49 State legal, mandrel bend mid-pipe with hi-flow cat converter
8. Dynomax Super Turbo Catback