The provisions of §§ 1.43-1, 1.43-2 and 1.43-4 through 1.43-7 are effective with respect to costs paid or incurred after December 31, 1991, in connection with a qualified enhanced oil recovery project. The provisions of § 1.43-3 are effective for taxable years beginning after December 31, 1990. For costs paid or incurred after December 31, 1990, and before January 1, 1992, in connection with a qualified enhanced oil recovery project, taxpayers must take reasonable return positions taking into consideration the statute and its legislative history.