EGR problems can sometimes cause idle issues. However, this will only happen if the EGR is stuck open. If it's stuck closed, or not operating correctly, it should not effect the engine idle. If however the EGR is stuck in the open position it will add exhaust gases at idle, upset the idle mixture, and cause an idle problem. Usually a rough idle. A quick way to check for this with the old style diaphragm EGR is to pull up on the diaphragm of the valve as the engine is idling. If the idle changes or the engine stalls, the EGR is working properly and is not the cause of the problem. You can also apply vacuum with a vacuum pump to the EGR valve if you can't pull up on the diaphragm in the valve. The results would be the same no matter what method you choose. If you have no change when you manually activate the EGR it could mean a couple of things. The first is that the EGR valve has failed mechanically and should be replaced. The other possibility is that the passages that feed the EGR gasses back into the intake are clogged and not allowing EGR gasses to flow into the intake. Either way, this is an EGR issue and should not effect your idle. If you have an electronic EGR valve, testing will be different. You may be able to activate it with a bidirectional scan tool to verify it's operation. This testing will vary depending on make and model and also if you have a scan tool capable of commanding the EGR to operate. It would be best to consult the service manual for the vehicle you're working on to verify EGR operation if you have the electronic type. As stated, the only way EGR effects the idle is if it's stuck in the open, or partially open, position.