Franz Tost has admitted that Scuderia Toro Rosso's form over the remainder of the 2009 F1 campaign hinges almost entirely upon the success of the technical upgrade package being brought to the table for next weekend's Hungarian Grand Prix.

The Red Bull 'junior' concern has endured a miserable first half to the year, with just five points on the board from the opening nine races, no finish better than seventh place and now a mid-season driver change, with record-breaking former multiple Champ Car king S?bastien Bourdais having been unceremoniously dropped, ostensibly in favour of reigning British F3 Champion Jaime Alguersuari.

The crux of the small Faenza-based squad's problems has been the poor performance of the STR4, which has limited Bourdais and team-mate S?bastien Buemi to the rear quarter of the grid more often than not, and has arguably now seen the team replace Force India as the guardians of the wooden spoon in the top flight.

Following a comparatively bright start, failure to keep pace with rivals' development has seen STR get left behind. Team principal Tost is adamant that such an unenviable situation has to change - and, moreover, that it will.

"Toro Rosso had quite a successful start to the season, scoring points in Australia and China and later, in Monaco, we picked up another one," the Austrian underlined. "However, from then on we lost touch with the other midfield runners.

"There are various reasons for this, Firstly, the other teams improved their cars, regularly producing updates to their technical packages. We introduced a few small updates, but nothing major. For example, we are the only team never to have run with a double-diffuser, one of the key elements to car performance this year. Why? It was a financial decision. Rather than incur the costs of constant updates, we chose to keep costs within budget by waiting before delivering one major update package, which will make its race debut at the Hungarian Grand Prix.

"Secondly, apart from the limitations on car development, we also had one driver who did not live up to our expectations. We expect that the technical upgrades should see us return to a level of competitiveness that we were able to demonstrate in the second half of last season."

Those sentiments were broadly echoed by STR technical director Giorgio Ascanelli, who suggested that the Budapest update is 'equivalent to the one Red Bull introduced at the British Grand Prix' - producing a car that enabled Sebastian Vettel and Mark Webber to storm to an unchallenged and dominant one-two finish at Silverstone.

"There are several factors why our performance hasn't matched up to what it was in the second half of last season," concurred the Italian. "Last year, within the limits of our own capabilities, we went down a different route to Red Bull Racing, particularly with suspension and a braking system that was different to their car.

"Last year we were also racing in an era where the technical rules had been more-or-less stable for a decade, so performance levels flatten out, making it harder to come up with something new. This year, the pace of development has sped up enormously, and as a small team we have been unable to keep up with that. Today, Red Bull for example is producing large steps forward in development on a monthly basis. We cannot do that, as we don't have the manpower.

"There is a view that the only difference between our car and the Red Bull Racing one is the engine, but that is inaccurate. It involves the engine, gearbox, clutch, hydraulic system, water, oil and electrical systems - and all this on top of the actual aero parts in terms of bodywork. The further complication is that, although we have not run it, our car was designed so that it could incorporate the Ferrari KERS system, and that is very different to the one used by Renault, around which the RB5 was designed.

"Therefore, we were not in a 'cut-and-paste' situation when it came to getting the parts. It was not a case of getting a drawing from Red Bull Technology and simply manufacturing it. The two cars might look the same, but if you try and fit the bodywork from one onto the other, it would not fit. The rear suspension is also different because, in order to maintain the same wheelbase, it needed a different arrangement.

"In Hungary we have a major upgrade, which includes the floor, rear wing, rear wing endplates, a nose which has had to pass a new impact test, new brake ducts etc - pretty much the whole damn lot! We've worked our hardest to get this modification package, and to do it this year is much harder than the work we did last year.

"Nothing stays still in this sport, though. It's not as simple as saying 'last year we made a technical step forward for the second half of the year and performed well, so the same thing will happen again.' Last year, the Italian media was keen for me to puff out my chest and say 'oh yes, I am very clever and I have managed to out-perform our Red Bull cousins', but I wasn't a genius last year, and I don't think I am an idiot this year either!"