Can a car run without an EGR valve

It might affect the environment but it is not harmful to the engine. Some people are running for more than 50k km without EGR. The EGR is disabled in all remapping.

What happens if you remove the EGR valve?

Removing the EGR valve will certainly remove a component that requires regular maintenance, but it will make your car less efficient, as well as committing a detrimental offence both to the environment and to other drivers and road users.

Can I disconnect my EGR valve?

Yes but not advisable. The egr can go bad two ways, stuck open or stuck closed. The egr recirculates part of the exhaust back into the engine intake system to burned any unburnt fuel the first time aroundto and lower the exhaust emmisions.