The car named for the Bonneville Salt Flats will return there this month in an attempt to break the land speed record. Pontiac Div. is taking a modified version of its Bonneville sedan to the Salt Flats (Aug. 12-18) for a go at the 209.21-mphStock Class land speed mark set in 1998. Thirty-year racecar veteran Mike Cook will drive the Pontiac, expected to be one of 300 entries taking a stab at the record. Modifications include tweaks to the 3.8L supercharged engine that will help squeeze 455 hp out of the venerable V-6 and addition of a parachute to slow the car down.