Red Bull was the first team to harness the concept in 2010 and last year optimised it to a degree that allowed it to dominate both the drivers', with Sebastian Vettel, and the constructors' championship.
Despite working to recreate such an effect in a limited way, which led to a rules clarification that forced Red Bull's Renault engine partner to modify engine maps designed to extract the most downforce available from blowing exhaust gases at aero-profiled brake ducts, Red Bull has won only three times this season.
While it leads the constructors' championship by 53 points, after 11 races last year it was 103 points clear.
"It's pretty much as we feared before the season started," Newey told AUTOSPORT.
"Having explored exhaust blowing technology quite heavily for two seasons and then having that taken away together with other changes like the front wing flexibility [test rules], hurt us quite a lot.
"Probably [it hurt us] more than other people because we had been exploiting it for longer. It has taken a while to try to understand what we need to do and to recover."
Newey also hinted that Red Bull has yet to re-adapt its car to the engine mapping rule change introduced ahead of the Hungarian Grand Prix at the end of July.
While Vettel was able to finish fourth at the Hungaroring, he struggled to match the race pace of McLaren and the Lotuses and the car was flattered by running on fresher rubber relative to the top three late in the race.
"We've been working with Renault and were suddenly faced with a clarification that was a different interpretation to what we thought we were operating to.
"That's where we are and we've got to go back and have a fresh look."