Nearly four years after the Food & Drug Administration warned Boston Scientific Corp. (NYSE: BSX) that it was on thin ice, the medical device maker says the federal watchdog agency granted absolution on all issues raised in a 2006 warning letter.

In January of that year, the FDA sent then-CEO James Tobin and chairman Peter Nicholas a stern missive warning that multiple inspections of six plants around the country revealed "serious regulatory problems involving your medical devices."

"The purpose of this letter is to apprise top management of your inadequate corporate-wide corrective action plan as evidenced by the continuing serious deficiencies identified at each of these facilities and to remind you of your responsibility to ensure that all facilities continuously comply with the Act and all pertinent regulations," the FDA wrote.

The problems involved a range of Boston Scientific products, from workhorses like its Taxus drug-eluting stent to its Leveen needle electrodes. Plants in Natick, Watertown and Quincy, Mass.; Maple Grove, Minn.; Spencer, Ind.; and Glens Falls, N.Y., all had "serious, systemic problems with your overall corporate quality management systems," according to the letter.

Current president and CEO Ray Elliott, who succeeded Tobin last year, said resolving those problems is a "major milestone."

"Quality is our highest priority and our greatest responsibility. While our quality work will never be done, we have revolutionized our approach and transformed our culture, and we are confident that our commitment to the highest levels of quality will create a competitive advantage for Boston Scientific," Elliott said in prepared remarks.