Do I have a illegal search and seizure case here?

Maybe, a wide turn is pretty flimsy for a reason for a vehicle stop.  That does not mean that the officer can't testify that he had a reasonable suspicion of a violation of the vehicle code.  These questions are very hard to answer without a more thorough intake and review of discovery.  You have two potential points of challenge, the stop of the vehicle, and the subsequent search.  The officer must articulate probable cause to search your vehicle, which they almost always say they smell marijuana.  Its an objective standard so its tough to challenge, but it can be successful.   Your best course of action at this point is to sit down with an experienced defense attorney.  Most attorneys worth their salt routinely litigate suppression on facts such as these and would be well versed in the current state of the law.  Trying to go it alone means you won't have the benefit of that training in experience.  These are highly technical arguments that require a good understanding of the current case law.  Do yourself a favor and talk to an attorney.