Luke Glendening 33 goals scored, 8 of which are ENG, basically every 4th goal he scores is an ENG, that's the highest ENG to goals ratio I could find..I'm sure there's probably someone who's scored 1 of his 2-3 goals ENG way down on the list but haven't gone through all the pages
Timander also got 3 ENG of his total of 13, at 23%
edit: went a bit further, and of 2 ENG or more Randy Bucyk got the highest ratio, with 2 ENG and 4 goals total...also see Duncan Siemens have scores his so far one and only goal as an ENG so he's got a 100% ratio