Haas switched Romain Grosjean back to a version of its Melbourne-spec Formula 1 aerodynamic package ahead of Singapore qualifying, with the driver saying his team faces a "big correlation issue".
After a tricky day of Friday practice at the Marina Bay circuit, Haas chose to revert Grosjean to the floor, bargeboard and rear wing package it used for the first race of the 2019 season, while sticking with the latest front wing.
Grosjean ended up qualifying 18th as he was knocked out in Q1, and said afterwards that "we just know that the windtunnel to the track has been wrong" when it came to recent upgrades.
"We were supposed to have a lot more downforce with one package but when we put on the other one, we were within noises," he continued.
"So it is something that we try to understand: where is it coming from?
"At the minute that is the key, getting the delta to a map at a more decent level [rather] than staying where we are, which is a big correlation issue".
But Grosjean insisted he doesn't think the team is "lost".
He added: "We just need to understand where it is and we know it is somewhere in there.
"There has been acknowledgement of it. Singapore is one of the hardest tracks and if you bring a race one package here, you don't expect miracles."
Although a lack of preparation time meant Grosjean could not extract the most from the Australia package ahead of qualifying, he is adamant the team has done the right thing with making its priority getting to the bottom of why its updates have not worked.
"It was not necessarily a request of mine but after practice we didn't have anything to lose, to just send it and see what it was going to do," said Grosjean.
"I think it was the right call.
"Unfortunately here because FP3 is not representative of qualifying and FP1 is the same, we just didn't get the time to set up the car properly.
"I think there is probably a bit more potential than the new one in it but we just ran out of time to set it up."