Petrol issues

Hi , I'm having a huge petrol issue with my mk1 caddy. £20 gets me 50 miles. Need some advise on what to do as I may aswell be running a hummer! It's got a 1.6 petrol engine btw

CHECK FOR LEAKS! all the way from the tank to the carb.
If there are no leaks, check and set cam timing, spark timing and mixture.
Pump up all your tyres to 34ish psi
Clear all the crap out of the boot and off the back seat
And the last thing to do is go easy on the right pedal!