I would suggest that you are already qualified by bases of your experience and IWE diploma, to perform inspections under AWS D1.1 criteria. In the latest edition of AWS D1.1 (2002), Paragraph 6.1.4.1(3) states: "An Engineer or technician who, by training or experience, or both, in metals fabrication, inspection and testing, is competent to perform inspection of the work."

Of course, as I said above, this only addresses the inspection aspect of the work. In your posting you didn't really say what certification adn/or training you were in search of. I would not be one to stear you away from seeking AWS Certified Welding Inspector qualification as it is easily one of the most recognizable certifications in the world.

Hope this helps, I'm sure others will also have their own perspective on your inquiry.