15 year-old Mitchell, from Claredon Hills, Illinois, piloted his #2 BGR/ Team Grote Piper DF-5 to the checkered flag in Saturday's 15 lap race, edging Johnston by 1.273 seconds at the stripe, with BGR teammate Jesse Lazare following in a distant third place.
Johnston exacted a measure of revenge in Sunday's feature event, drafting past Mitchell on the penultimate lap to take the lead and the eventual victory.
"I knew I was fast, it was a matter of waiting for my hole," explained Johnston. "It started to rain at the end, but I put my head down and went like hell."
Johnston, who secured the Canada Cup trophy with her victory, took the checkered flag .370 second ahead of runner-up Lazare, with Mitchell a further .185 seconds in arrears, in third spot.
The doubleheader F-1600 weekend also marked the first time in Ontario that Honda powered machinery had swept the podium positions.
POITRAS CLAIMS FIRST WIN OF 2012: While his primary division rivals were eliminated from the June 30 Paragon Competition GT Challenge event due to mechanical issues, the #117 Corvette of Kevin Poitras suffered no such problems as the Newcastle, ON resident scored the overall, and GT-1, class victory at Canadian Tire Motorsports Park.
"That was long and hot. Once the (Krikorian brothers) Subarus and (Ian) Patterson dropped out, it became a strategy game. The track got pretty slippery towards the end, but I had enough room to back off to about 80% to save the car," explained Poitras.
Andrew Romocki and Ian Patterson both retired from the one-hour event while leading in the overall standings, Romocki's Corvette suffering from power steering pump failure on lap 14 (of 40), while Patterson pitted with just five minutes remaining due to a bad vibration following a Turn Five spin.
Poitras took the checkered flag in the timed contest a full lap in front of GT-1 runner-up Allan Lewis. Russell Saulnier, making his first start of the 2012 season, claimed the GT-2 class honours while other division winners included Scott Tapley (GT-3), Dylan Gibson (GT-4) and Andrew Cordeiro (GT-5).
By J. Wally Nesbitt. Watch for extensive coverage of these events and more in the next issue of Inside Track Motorsport News.