Big air leak like that will mess with the fuel trims as the exhaust sensors pick up the unmetered air that has not been measured by the Maf. It thinks its running lean and demands the injectors to increase the fueling, it will do this by adding up to 20% more fuel in effort to correct the seen lean mixture. Thats why you are smelling petrol, once it realises its not correcting the fueling it should set a fault code and light the EML to draw attention to the fault. If you have some decent diagnostics you can view the fuel trims and see what they are doing. Ideally you should be seeing near enough 0% with an engine at running temp and at idle. High fuel trims are usually down to air leaks in the vaccum system anywhere across the engine. Best method of finding air leaks is a smoke test some are not as obvious as the split you found in the intake boot, other areas not to be ignored are the cam cover, dipstick tube for a failed O ring and blanking caps on the rear of the inlet manifold, these perish and split which results in them falling off and introducing an air leak. The tiny vaccum pipes at the front of the engine also perish and fall apart, 3mm silicone vaccum pipe is a good replacement for the rubber type.
With a completly sealed vaccum system you will notice an improved mpg and have less visits to the fuel station.
