New pieces, including a new diffuser, were tried in a straight line at the Idiada facility in Spain, prior to the US grand prix.
It was rumoured immediately afterwards that the real-world data did not match up with what was produced in the wind tunnel.
Still, the new diffuser was fitted to Spaniard Alonso's F2012 in Austin, before he was roundly out-performed by teammate Felipe Massa all weekend.
"Yes, indeed, Felipe Massa had the old diffuser and it worked better," former Toro Rosso driver Jaime Alguersuari told the Spanish sports daily AS.
And Brazilian Massa confirmed to Marca newspaper: "Everything was the same except the diffuser.
"I had it available, but I decided I'd be better with the old one. That was the only difference."
Alonso said "It's not always the case that the latest part is the best choice".