The Wasps back kicked four goals from as many attempts against Doncaster in the Championship Cup, including the conversion which secured at 20-18 win.
He played at centre in that game a week after starting at full-back against the same opponents and landing six goals, also without a miss.
The 20-year-old is one of 12 players – three of them on loan – brought in to strengthen Carnegie’s squad ahead of their return to league action at the end of this month.
The arrangement works both ways and he said: “I am enjoying it, it’s really good.
“It is good to play week-in and week-out. It has been a while since I’ve had four games on the trot and I’ve had some decent minutes.
“They are a good bunch of boys and it was a good hard-fought win on Saturday.”
Umaga, a specialist fly-half, has been in eye-catching form for Carnegie, but insisted: “I just try and help out in the game as much as I can.
“As long as we get the wins at the end of the day, I am happy with that.”
After one win from their opening nine league games, Carnegie have three victories from five in the cup.
“These cup games have been a big statement from us,” said Umaga. “We are trying to build momentum back into the Championship so if we can keep winning and keep playing well that’s all we can ask for.”
Carnegie had three players sin-binned in both fixtures against Doncaster and hit back from 10-0 and 18-10 down last weekend.
“We were down to 13, but we stuck at it,” reflected Umaga. “Credit to the boys, they did really well.
“We had three backs at one point in Saturday’s game so we were covering the whole pitch, but it was a great game to be part of.
“The coaches said it was one of the best wins we’ve had in a while for this club, to have the grit and show what we can do.
“I definitely think the vibes are getting a lot better and the boys are getting a lot stronger and closer together.
“We are trusting in each other now we are getting a few wins on the trot and we are trusting in the system as well.
“The boys are outstanding and they have welcomed all us new boys really well. It is a good place to be at the moment.”
Wasps are expected to recall him later this month, but for Umaga, joining Carnegie has been like coming home.
He is the son of former Halifax rugby league and Rotherham union star Mike Umaga – and nephew of All Blacks legend Tana – and played his junior rugby with Old Brodleians.
He had a spell with Auckland – as well as having played for England at Under-18s and Under-20s level – and is seen by Wasps as an important part of their future plans.
Ahead of Carnegie’s trip to Nottingham in the Championship Cup on Sunday, Umaga continued: “I was born in Halifax and my mum’s from that area. I know this part of the country quite well and it’s nice to be close to my roots.”