Pie throws, singing mailmen and free antacid tablets greeted frenzied procrastinators rushing to meet the midnight deadline for filing their federal income tax returns. Post offices across the country were open until midnight Friday to place the all-important April 15 postmark on tax returns, or on envelopes containing Form 4868 requesting an automatic four-month extension of the deadline. Paul Monroe, regional manager for H&R Block in Boston, said he sees the same people every year. ``They look forward to the excitement of April 15th. The adrenalin starts flowing,'' Monroe said. ``It's like a non-contact sport.'' In New York City, thousands of people crowded the main post office. Many spread their receipts on benches, tables or the marble floor, nervously glancing at the clock until they finished, then heaving a sigh of relief, their faces glowing. Free antacid samples were distributed outside, and a toy office opened an ``IRS Stress Relief Clinic'' which invited frustrated taxpayers to come in and yell at a dummy. ``This is insane,'' John Zoilo said as he slaved over his returns. ``The last time I felt this harassed was when I got married, and that's why I'm now divorced. ``But I must admit, there's no better place to do this if you're going to be late than the Eighth Avenue post office,'' he said. ``You're among thousands of procrastinators.'' New York's Internal Revenue Service center expected to be deluged with about 2 million tax returns today, said IRA spokesman Neil O'Keefe. Another half-million people were expected to file for extensions. Nationwide, the post office expected to handle 30 million tax returns in the final days before the deadline, said Postal Service consumer advocate Ann Robinson in Washington. Returns not postmarked by midnight could be subject to a late filing penalty, possibly up to 25 percent of the taxes owed. Last-minute tax filers backed up traffic for several blocks near Chicago's Main Post Office Friday night, but other taxpayers got a chance to vent their anger at the IRS by throwing pies at a mock IRS agent. For $1 or $2 a pie, passers-by tossed whipped-cream concoctions in the face of Scott Goodman, part owner of the Superior Street Cafe, who posed as IRS agent ``Shirdolph Yurback'' to raise money for charity. ``You know what I'm going to do with your taxes?'' he asked one passer-by. ``I'm going to fund a study of South American insects.'' The woman stopped, plopped down $2 for a large pie and slammed it at point-blank range into the mock agent's face. ``That felt great,'' the unidentified woman said. At a post office in Springfield, Mass., postal worker Bill Mannila entertained tardy taxpayers by lip-syncing ``Return to Sender,'' while dressed in a costume that was half Elvis Presley, half regulation grays. A six-piece band of postal workers also was on hand, joined by a postmaster who belted out ``Pennies From Heaven'' and ``King of the Road.'' ``It's like a zoo, but it's fun,'' said Springfield Technical Community College Professor Bill Herd, who along with colleagues and students helped taxpayers fill out more than 100 forms. ``People are not so mad about paying their taxes. They come in here with a frown and they leave with a smile.''