Fergie, welcome to our little community and invite you to call this home . . ..
What I'm reading sounds like a build-up of creosote (oily substance from cooking with wet or soaked chips ).
You won't have any problem with it other than a bit of a bitter taste, sauce helps here...
Guys help me if I am wrong ... The amt. of carcinogens on the meat is negligible and is a product of cooking for long periods as in slow smoking ... or the amt of "White - off colored " smoke during the cook... you want a light 'bluish' colored
smoke , a cleaner burn . Bitterness will decrease dramatically and the food will have your nice smokiness you want... What you have done (wrapped and in the over) is a good way to finish the meat and with 4 hrs. of smoke on it you
should be good to go , smokey , but not bitter... Your biggest mistake was soaking the chips . You need to set the chip pan away from the burners , and preferably in a "Non-Gasser" , to smoke -not smolder , only partially burning the wood products
thus giving the white smoke ... Slow down and let the smoke turn blue and continue .
Your smoker woes can be fixed with a trip to Craigs list and looking for a 'Smoker" either charcoal or wood burning . They are usually cheap ( sold by some poor dude that got Jaded with the work in getting a good smoke the first time ... don't work
that way ,you got to practice to get proficient at your cooking . When we ( as a group ) started , we had miserable out comes in the first cookings , however , with the help of a "Cooking Log Book" and practice , you'll become a good / better cook.
Take the first smoke with a grain of salt . . . and keep trying . My "Matra" is PATIENCE , and will hear me mention it a lot . . . BBQ is , to me , a laid back , enjoy a beer , and relax type of activity. (Coffee if you don't drink , like me) .
Send some Q-view of your deeds , and tell us what you did . A lot of really good Smokers here and the help is only a keyboard away...
Have fun and as always . . .