Pye made his debut in the 2012 enduros, stepped up to full-time competition with Lucas Dumbrell Motorsport the next year and joined what was then Dick Johnson Racing in ’14 for three seasons.
Squeezed out for Scott McLaughlin, Pye moved to the Holden squad at the start of last year, finishing 12th in the championship.
Inheriting the race lead when McLaughlin went off at the start of lap two, Pye controlled proceedings through the pitstops and as rain started to fall in the closing laps.
A mistake at Turn 13 on slicks with three laps to go nearly cost Pye the win, but he did enough to keep Whincup at bay.
“Sometimes the opportunities can be few and far between,” Pye said.
“And when you get one like [Race 5], it’s something that you spend your whole career preparing for, you’ve got to capitalise on it and you’ve got to make sure you get that win when it’s there for the taking.
“To have someone like Jamie behind me and in those conditions just makes it a very special moment. I think it’s one that I’ll remember forever.
“I don’t know if it will be my favourite win into the future, but certainly that’s the best I’ve had in a race car till this day.”
Pye’s victory means 19 of this year’s 26 full-time drivers have won a Supercars race.
It follows a strong start for the newly-established WAU alliance in the season opener in Adelaide, which James Courtney and Pye left third and 10th in the championship.
Courtney had a tougher run in Melbourne, but Pye moves up to fifth, having finished sixth, 11th and fifth in the other three races aboard his Mobil 1 Boost Mobile Racing Commodore.
“Every time we’re at the track we just have to keep trying and keep improving the package,” Pye added.
“It’s so competitive at the moment and if you’re not moving your own yard stick, then the others will overtake you.
“It’s forever moving forward and that’s what other teams in the pits have been good at in the past.
“Now we have some momentum and I feel extremely happy with the package we’ve got, it’s only one percenters and we just want to stay in that top 10 and get a great result week in and week out.”