I fitted an EGR bypass a couple of weeks ago and then broke down on the motorway last night
The car had an engine fault light (I think that's what it said) and would only run at about 1400 revs.
Looking under the bonnet, the EGR pipe had split and was blowing hot gasses onto the inlet manifold. You can see from the photo that it's melted some of the plastic.
I think it's melted some of the wire there too, which is the MAP sensor I think. I assume that's what was causing the engine fault.
I bought this type of bypass because I'd read that it puts less stress on the pipe - and I was careful when fitting the blanking plate. I guess the pipe was just getting weak and me messing with it has finished it off.