Heat your oven to 250 degrees F
Spray a 13" x9" baking sheet with non-stick cooking spray
Combine cereal and pecans, mix thoroughly, and spread evenly on sheet and set aside
In a large microwavable bowl, combine brown sugar, corn syrup, and butter.
Microwave mixture on High for 1 minute and 30 seconds
Stir completely and microwave for another 30 seconds until it is boiling
Add the vanilla and baking soda and mix completely.
Pour the mixture completely over the cereal and pecans stirring the mix with a spatula to ensure everything is coated
Bake for 1 hour at 250 degrees F stirring every 20 minutes spreading the mix over the baking sheet
Allow entire mix to cool, break into pieces, and store tightly covered.