http://velonews.competitor.com/2011/06/news/the-explainer-that-questionable-tour-de-france-podium_176880This article gives a summary of the suspicions and implications of every TdF podium finisher from 1996 to 2010.
Conclusion: only very recent finishers have not been implicated.
Only Cadel Evans, Andy Schleck, Carlos Sastre, Denis Menchov have no evidence to implicate them. Wiggins is too new on the scene to have been mentioned in the article, but he seems to be in the same boat as Cadel and Schleck.
This is also a good article
http://www.sportsscientists.com/2012/07/tour-in-mountains-analysis-discussion.html...explaining exactly how much slower the tour has gotten, and estimates that:
"So, in terms of what that means for Wiggins and co at the front of the stage, it predicts about 6.4 to 6.5 W/kg. Over 16 minutes, that's not at all unreasonable. To give you some context, calculations of climbing power output in the Tour de France in the 1990s and 2000s often estimated that top riders maintained power outputs of 6.4 to 6.5W/kg on the Tour's HC climbs, most of which take over 40 minutes to climb."
"You're predicting physiology that says that the world's best cyclists have a VO2max of 85 to 87 ml/kg/min, that they're 23% efficient, and riding at 90% of maximum. Or, they could be 24% efficient with a VO2max of 81 ml/kg/min. That is, on paper, normal physiology for the best cyclists in the world in peak condition.
The "abnormal" physiology of years gone by came from guys who were sustaining 6.4W/kg for 45 minutes. That points to a human that has a VO2max of 97 ml/kg/min on the bike, or an efficiency of 28%, or can sustain 95% of max for 45 min at the end of five hours of racing. That just doesn't happen."