Two tax changes affecting US oil and gas companies under discussion as ways to lower the federal budget deficit would cost the government more money than they'd raise, according to a new study.One of the changes would prohibit oil and gas companies from using the manufacturer's deduction created by Section 199 of the American Jobs Creation Act of 2004. The other change would create new limits on foreign tax credits by US dual-capacity taxpayers, which—like international oil companies—deal with a foreign country as both a sovereign and provider of economic benefits.The Obama administration has included the changes in each of its annual budget proposals. Lawmakers recently have ...