Since NASCAR put them on suspension in June, Chad Knaus and Steve Letarte have managed to stay busy. That hasn't kept the two Nextel Cup crew chiefs from being frustrated. "I'm not going to lie to you, it's tough," Knaus said Friday after rejoining reigning Cup champion Jimmie Johnson and his No. 48 Hendrick Motorsports team to prepare for Sunday's 3M Performance 400 at Michigan International Speedway.