You bet the timing is way off retarded. Now please don't think I'm calling you out as retarded cause I'm not. White smoke and stumbling tells me you can advance the timing about two dimes thickness. Thats about 4 degrees. You really need to find a compendent shop to time the engine. Never allow a shop to time it by ear. If your paying good money for timing by ear please send me the money and I'll tell you your truck sounds great for my ears work.... Thats all a shop is doing for you... Plus robbing you of some cash. Only one member here has ever timed by ear and it happened only once but... Mel has timed probably 200+ engines for others in the last 10 years.... Thinking about it now I bet I'm really low on my estimate. He even tells us he got lucky with that engine...
Been more than one, I timed mine by ear a year before I ever had a meter! Lucky, maybe, but I've timed probably 1000 engines in my life and Pete told me what it should sound like! That was god knows how many years ago and while I've checked the timing 100 times (testing meters and such), it's not been changed since! That being said, timing it with the proper equipment will be much easier! lol
I've always timed gassers with a meter and then adjusted them, I timed my 6.9 by ear and then played with it, but always found where I originally set it to be where it runs best, and that's where a meter says it should be (well about 1 degree advanced of what a meter says it should be).