Sounds like you got a bum bag of wood, there is no other reason that pecan wood would be overpowering. Pecan is one of the mellowest hardwoods, 10x mellower than mesquite wood, you got some tainted or miss marked wood. I thought I hated hickory after trying it out of the same bag on a few smokes, it was nasty.
Years later I'm at a buddys house, and he's smoking a brisket using hickory, I'm thinking that it's going to be nasty seeing how much wood he's rolling through on his offset cooker. Nope I was way wrong it was the best brisket I ever ate. Since then I use hickory all the time and have never had that nasty taste like the first time I tried it.
Also, have you checked the inside of your cooker to make sure it isn't covered in creosote? That could be another reason you'd get a funky taste off of pecan or any other wood. Get your smoker nice and hot and get in there and wipe down everything inside with some old towels then hose it out while everything is nice at hot. After you clean it out get it hot and reseason it again then cut a couple onions in half and rub down the whole inside of your cooker with them.