Both Asmer and Mustonen made efforts to pass Hohenthal but the Swede kept his cool.
Michael Devaney scored the best result of the season so far for the Ultimate Motorsport Mygale with fourth place ahead of Niall Breen and Stephen Jelley.
Asmer now has 189 points to Maro Engel’s 111 and Sam Bird on 106. Bird took the lead at the beginning of the race but had to serve a stop-go penalty after stewards declared he had jumped the start.
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