Hello im here in Brownwood TX. I have a 97 dodge 3500 cummins 12 valve 5 speed. iv had the truck 6 months when i got it seemed to not have much power. like when you would pull a small grade it would go from 65 to like 55 well changed the filter and cleaned the prefilter seemed to helped some. well i turned the star screw up quiet a bit its a lot better but some times it catches like when im at a light and shift from 2 to 3rd it will just take off like a race car. and blow black smoke but it does not run that way all time it does the smoke thing once a week or so a friend of mine says his will do it all the time. witch i dont want the smoke but would like the power well i was looking at the overflow valve and it does not appear to ever have been changed. it has 223000 on it. I am disabled . is the overflow valve hard to change and where is a good place to get one. well sorry for the long thread and thanks for all the help my number is 325-721-8661 call or text or send me a pm if you can help or know something to change thanks again!!!