"Unfortunately all the tricks I had in the past [car set up] aren't having the same effect this year. There's been a big change in the tyre that's been hard to get on top of.
"We've had a few good races but, on the whole, it's been a bit disappointing performance-wise."
The GP2 championship has always had the reputation of being one of the tightest fought series and this year is not much different. No single driver has pulled away from the chasing pack with only one driver inside the top 10 having picked up points at each round.
Italian Raffaele Marcello (third) has managed to score each weekend, with the rest of the drivers vying for the title having come away at least once with nothing to show.
"There are a lot of points left in the series and I can still be in the championship fight, but we need to pull our finger out a bit to fight these guys at the front. They are super, super quick.
"There are probably three drivers - Gasly, Sirotkin and Giovinazzi - who are becoming consistently quicker than the rest of us. Somehow they are on a different level and have risen to the top after a rocky start to the season."
Evans likes Spa and has had a fair amount of success at the Belgium track in the past. It's a difficult circuit to get right and always puts on a great show with its two long straights and tricky infield with its elevation changes making the cars work hard.
"I hope we can come away with a result this weekend. We've got a few changes we're going to try and get us into a better position in the championship.
"I enjoy Spa and I've had some good success here with podiums and a pole in GP3 and I had a good race last year. It's good for my confidence that it's been a good track for me," said Evans.
While still keen to grab a GP2 title to go with his GP3 championship from 2012, Evans has been keeping his options open and tested this week with the new Jaguar Formula E team at Donington Park in England.
"Jaguar got in touch and the Formula E test was a really interesting day. It was a tricky little car to get used to at the start. There's a lot to take in with all the technology, which challenges the driver quite a lot.
"I hope it's not the last time I get to drive it.
"It was a solid day and I'd never been at Donington before so it was good to learn another circuit.
"I'll have to wait and see what they think. It would be great if it worked out, to be aligned with a manufacturer would be incredible," he said.