If the codes have been cleared no fault codes will come up at least untill the engine/ car is run again, perhaps for a few miles or until the conditions that generate the fault code happen
EGR stands for Exhaust Gas Recirculation, there is a "hole"/ connector on the exhaust manifold, close to the exhaust port of the 2nd cylinder from the left, as seen standing looking back with the bonnet open - i wondered if this was the faulty cylinder, and speculated if this was somehow connected in some way and it was not a coincedance that the faulty cylinder/ injector was the one connected to the EGR
that 2nd cylinder / part of the exhaust manifold, connects to the EGR cooler, it then goes into a metal pipe, which goes around the engine block/ head (on the right-hand side) before connecting to the EGR valve housing on the front (left-hand-side) which connects to the inlet manifold