HPLaserjet 4350dn has fuzzy text on printouts intermittent problem on various stock.

When the print job comes out, can you actually rub the toner off the page? If you get smearing or toner not fusing to the paper the dc controller PCA could be defective because it controls the fuser roller temp.

Have you completed a half-print test page, or stopped a print job as the paper is passing by the toner cartridge?  If you do, you should be able to see if the drum in the toner cartridge has the image defect on it or not.  This would help isolate if the problem is happening in the development area, or as the paper is moving towards/through the fuser.

no it's fused perfectly.  It's intermittent, so I don't think it's the toner plus thats been changed as well as the fuser assembly.  I suspect the formatter board but I'm not 100 percent sure and was wondering if there were any known issues that I did not know about.

It almost seems like the laser might be vibrating when writing the image, because it looks ever so slightly blurred but darker like it was double stamped slightly askew.

I also set the toner density to the lowest setting.  I might add that it seems to be only on random words, however on multiple copies it will be the same words each page.  

A worn scanner motor can cause imaging issues, have you tried cleaning the slit glass on the laser? debris on the glass can cause charge problems on the toner drum.

Have you checked to see if the image defect is on the drum?
You also mentioned double-stamping in your original post, do you mean that the printer will print the same image repeatedly down the page sometimes?  If it is, how far apart are the repeat images?

By double stamping I mean it looks like the text is being printed twice to the same exact spot, however slightly thicker than the other text on the page.  Like it was printed twice and slightly overlapping.  I've not cleaned the glass on the laser yet, that sounds more like the area but like I said it's intermittent.  I think it might be vibrating at certain intervals durring the writing stage, and as a result it may be blurring the image or text slightly.  Personally I could live with this type of issue, however the client for which the service is being provided is a little more fussy.  It's not a repeating pattern.  It will however repeat on multiple copies.  So if the 7th word on the printout is blurry, you can be sure that the same word is blurry on all printouts of the same document.  (At least the ones that were printed off the same image.)  I hope this is helpful and sorry for the delay in responding from last night.

Same words on the same document on different copies indicates to me the printer is printing what is told. I would look at the driver or application. Are these words supposed to be bold or italics?

Does it happen on any of the test documents built into the printer? Configuration pages or error logs?

Nope that was the first thing I looked for, bold text on docs.  I'm starting to think it's firmware related.  Will try updating next time I'm there.  It doesn't happen on configuration or test pages.  The only thing I can think of is something is happening durring the writing stage that is causing this.  

It sure sounds like some text property(bold, italics, different font or colour) that is messing it up.