Michael Laverty narrowly missed out on scoring his first MotoGP points as the Northern Irishman rode an impressive race to finish 16th in Austin.
Laverty, riding the PBM-built Aprilia, dropped to last on the opening lap after hitting a false neutral that forced him to run wide.
Undeterred, the series newcomer re-joined the race and battled through the field to climb to 17th place by lap nine, before improving one place to 16th.
Laverty held his position to finish ahead of fellow CRT riders Hector Barbera and Hiroshi Aoyama to finish fourth in the Claiming Rules Team category as he continues to make strides with the PBM racer.
“I've got to be happy with this weekend but I'm left wanting more as a mistake on the opening lap when I selected a false neutral put me off track and dead last,” he said.
“I fought back through to 16th and fourth CRT so it's a big improvement on Qatar.
“My goal for this weekend was to hassle the FTR Kawasakis and in the race I caught, passed and pulled a gap on them all so I would say we exceeded our target for round two,” added the former Brtish Supersport champion.
“We have taken a big step forward with the PBM bike, time was always against us coming into the season but now we are making inroads with our base settings for the chassis and electronics, and I believe we can take another step forward in Jerez as we now have a clear direction on where we need to improve.”
Laverty's team-mate, Yonny Hernandez, finished 15th overall and third in the CRT class on the PBM ART.
The Colombian was overtaken by Randy de Puniet with two laps remaining after losing grip as his tyres went off in the latter stages of the race.
“I was able to battle with two prototype riders, [Ben] Spies and [Bradley] Smith, for almost half the race, but then my rear tyre performance dropped and I could not maintain the lap times,” he said.