I just removed the flex pipe section under the car and replaced with a section of just straight tube,im now having a vibration at very low rpms,could this be becaue i needed the flex section under the car or ???

Usually they flex section just off the engine is there to help reduce vibration down the exhaust pipe. I would bet that changing that has caused your new vibration. But you might check all your exhaust hangers and give the pipe a good shake and see if it bumps on anything.

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That's my guess.

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83 SD

84 CD

Will do,will report this week.
Thanks