More than four years later, and who-knows-how-many millions of dollars spent on remediation, Boston Scientific (NYSE: BSX) has finally fixed all of the Food and Drug Administration's issues with the company's manufacturing plant cited in a 2006 warning letter.

Yay, team!

Not really. Since the announcement of the warning letter, the company has lost more than 75% of its value; the S&P500 is down just 14% over that timeframe. The entire decline isn't due to the warning letter, of course, but it's a sign of the horrible four years Boston Scientific has had.

While the letter was outstanding, the FDA held up new product approvals including Boston Scientific's drug-eluting stent Taxus Liberte. The delay allowed Johnson & Johnson (NYSE: JNJ) to continue to compete with Boston Scientific's older stent and gave Abbott Labs (NYSE: ABT) and Medtronic (NYSE: MDT) time to catch up. The company cleared up enough of the issues to allow the FDA to approve the stent in 2008, but the damage was already done.

Besides an artificial cheer from this Fool, Boston Scientific doesn't gain much from resolving the warning letter now. In theory, it could give investors confidence that Boston Scientific is back on track, but considering it had a recall earlier this year for failing to file paperwork with the FDA, I'm not sure investors should read much into it.

Boston Scientific is extremely cheap right now, but that doesn't mean it's a good investment. The company is in the midst of yet-another restructuring, and figuring out when the last shoe has finally fallen will be difficult; just look at Genzyme's (Nasdaq: GENZ) ongoing manufacturing problems that are now expected to take up to four years to fix.

Insider buying would be one sign that things may finally be back on track, but the last major open market purchase by management was this time last year at much higher prices. Investors would be wise to follow management's lead and hold off investing until it's clear things are turning around.

Interested in profiting from declining companies? Drop your email in the box below.

Johnson & Johnson is a Motley Fool Income Investor selection and the Motley Fool Options recommended buying calls on the stock. Try any of our Foolish newsletters today, free for 30 days.

Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool owns shares of Medtronic and has a disclosure policy.