The special inspector for taxpayer bailout funds is looking into whether the Obama administration pressed General Motors in bankruptcy to backstop the pensions of the union retirees of a former division, Delphi. The inquiry could clarify a lingering mystery of GM's forced restructuring last year: Both unionized and white-collar workers earned pensions while at Delphi, a GM spinoff also in bankruptcy, but when the federal government took over their failing pension plans, only Delphi's white-collar retirees suffered painful benefit cuts. Neil M. Barofsky, the special inspector general for the Treasury Department's bailout programs, said he intended to find out 'whether political considerations played a role in favoring hourly over salaried retirees.' The federal government insures traditional pensions, but its insurance has limits, including, for example, a yearly maximum benefit of $54,000 for a person who is 65 years old when the plan fails. Workers whose companies promised them richer benefits can therefore suffer sharp reductions. Normally, no amount of complaining, lobbying or litigation can make the Pension Benefit Guaranty Corp. bend the rules. When Delphi's pension plans were terminated last year, many of its 21,000 white-color retirees were warned that their pensions might be cut by 30 percent to 70 percent. The amounts vary because the insurance rules involve factors like each retiree's age and years of service, the design of the pension plan and even how much money was in the pension fund when it failed. It can take more than a year for the corporation to calculate the precise amounts. While the white-collar workers waited for bad news, they learned that their blue-collar brethren would not have any pension cuts. Members of Delphi's three unions would get special payments called 'top-ups,' paid by GM's pension fund, to restore whatever the corporation took away. For more than a year, the white-collar retirees have been seeking help in the courts and through members of Congress, demanding to know whether the corporation was right to take over their pension plan and why union retirees got a much better deal. 