CAVE CREEK, Arizona — The new Toyota 86 has been renamed GR86. That’s pronounced GREAT-6. I took it to the flowing turns, blind hills and uphill straightaways of Cave Creek, 50 miles northeast of Phoenix. It’s a sports car’s natural habitat and the ideal place to explore the significant upgrades Gazoo Racing (thus the GR prefix) has made to fix the flaws of this wonderful, affordable toy: 1) A bigger, 2.4-liter Boxer-4 cylinder engine for more torque out of the twisties. 2) Stickier, wider tires for more cornering confidence. 3) Racier, upscale design to make the $100K sports car crowd jealous…