Force India deputy team boss Bob Fernley says the correlation issues that have impacted the outfit's performance since the beginning of the season are not yet fully resolved.
The Silverstone-based outfit had a rather laborious start to its 2018 campaign, tracing its relative lack of pace to a correlation discrepancy between windtunnel and track data, with the VJM11's bargeboard design mainly called into question.
The car's form improved for the Azerbaijan Grand Prix, where Sergio Perez conquered a podium finish, but Baku's specific layout and the misfortune of others also lent the Mexican a helping hand.
Force India's upgrade package for Barcelona will hopefully address its car's aero troubles, but Fernley insists the updates won't provide an overnight cure.
"Feet on the ground, we've still got a little way to go," Fernley told Autosport.
"We're not quite there yet. We've not addressed all the correlation issues that we had in Melbourne, but we're on the way to it.
"We shall still have some issues in Barcelona, it's not going to be all plain sailing."
Force India COO Otmar Szafnauer is equally cautious ahead of the Spanish Grand Prix weekend and is uncertain to what the degree the team's mods for Barcelona will iron out the VJM11's problem.
"I don't know how much of the problem we'll fix with the stuff coming in Barcelona, because there is a lag between finding a problem and actually getting the stuff onto the car," Szafnauer told Autosport.
"You always bring updates that the tunnel and CFD have given you an indication are going to be better than what you have now, and by a significant amount. But that's not reality," he added.
"So you've got to bolt them to the car, see if it correlates. If it doesn't, you have to understand why.
"Sometimes it doesn't because you haven't optimised the car on track yet. You have to spend time with those parts, just optimising around them.
"I remember Mercedes one year were saying they stopped developing their car with six races left, so they put nothing more on their car.
"And it just got faster and faster and faster, because they had a stable platform that they understood and they could work on making that platform go faster.
"If you're changing stuff all the time that's not good either, because it mixes up your understanding."