Just had it in the shop due to check engine light on. tests revealed it was an ERG Valve (?). They have installed 2 and the check engine light keeps coming back on..any ideas? there are no other error messages when they do the diagnostics.

some have a buildup in the egr passage way ! & some have a screen that gets clogged.

Start by checking the vacum lines going into the EGR valve, make sure all the vacum fittings are tight.