The International GT Open is a grand tourer-style sports car series founded in 2006 by the Spanish GT Sport Organisation.
It is a spin-off from the Spanish GT Championship, except its races are held internationally.
The team have made a slow start to the season, as they haven't had time to test anything on the car.
Before the opening race at Paul Ricard, France, the drivers ran in-and-out-laps to test parts. They didn't tweak anything to see how to get the best out of the car.
The weather was appalling and Van der Drift was punted off early in race one.
The pair were going well in race two until the crew couldn't get a rear wheel off during the first pit stop.
This cost them a lot of time, and because they were able to replace only three wheels at the next stop, Van der Drift had to race with a badly worn tyre.
Heading to Portimao the team weren't expecting too much because the crew had to repair the heavily damaged number one car after its shunt at Paul Ricard.
"It was a bit disappointing," said Van der Drift. "We had a bit of testing after the first round but didn't really learn anything so we struggled the whole time.
"We just can't get the tyres to work properly and we were down to the canvas a couple of times."
Razia started the race in 18th position and held that. Van der Drift hauled the car up to sixth but was penalised for an early pit release (all cars are held after a pit stop for the same amount of time).
Race two was no better, as the Kiwi was punted off again and rejoined the field in 21st place. After some great driving, Razia and Van der Drift managed to bring the car home in fourth spot.
"We did really well but the car is underpowered compared to the rest of the field," said Van der Drift.
"We're working with the McLaren people to try to get some more grunt."
The class has a "balanced performance" technical rule to try to even things out across all the manufacturers. As the McLaren is turbocharged, its boost has been cranked way back and it is down on power compared to the Ferraris, Porsches and others, which are conventionally aspirated.
"It's easier to de-tune a McLaren than a Ferrari or Porsche," said Van der Drift. "During the race we're a bit of a sitting duck so we have to get a bit more horsepower out of our thing somehow."
The next round is at the Nurburgring, and Van der Drift is confident the McLaren techs will be able to find some more get up and go for it.
GT Open Championship calendar
Round 3, June 1-2, Nurburgring
Round 4, July 13-14, Silverstone
Round 5, September 7-8, Spa-Francorchamps
Round 6, October 5-6, Monza
Round 7, November 9-10, Barcelona
