Fit a turbo, that'd get more air in
Seriously though, you've got a choice of either leaning the mixture out to correct the AFR or..
find a way of getting more air into the engine.
Obviously, where you are, you're in no position to fit a stage 2 or anything like that so either snorkal removage or lean out whatever fuel mod you've got fitted.
Failing that, I'd also be inclined to check the main air filter, make sure it's not full of crap because that wouldn't help matters either.
If you're not bothered about noise, remove any DB killers in the exhaust too as they'd help the engine breathe a little better and let more air through it.