Gas prices suck! I have a 94 Bonneville SE with 134,000 miles and still runs great. I monitor the gas consumption and mileage constantly. With the gas prices going up, ( No news here). Are there any reasonable mods to be made to improve gas mileage. I am currently at the 21-22 mpg range and would like to get better, as always. Thank you.

That'* right in the area you would expect. But you can check your tires, put in new spark plugs, wires, and coils if those are still original. Make sure the transmission has good fluid. Remove anything from that car that'* not needed to help save weight.

X2 on check the tires. Make sure the engine is properly tuned and the wheel alignment is correct.
Your mileage sounds about right for the car so I don't think its much off tune, but it never hurts to check.
Otherwise improving mileage is up to how you drive the car, a light right foot pays dividends. I just got back from a trip to visit my sister 300 miles away. Going there I was in hurry so I put my foot down and had to stop for gas after 250 miles, returning I cruised at 60mph and made it home with the tank still a quarter full. Both journeys took roughly the same amount of time, stopping for gas cancelled out the time I saved by driving faster.

K&N drop in replacement filters work as advertised, ive put them in every car ive had and always see improvement in mpg. ive started using e3 plugs on just one car and didnt get the power increase but gained some more mpg and they have run smooth for about 70-80k now. on my monte i get 36mpg hwy not trying and a peak 38 a couple times when really trying.