I have been tuning on my truck and have been fairly successful so far. But, it is going into regen every tank of fuel which is 400 miles. The mileage has gone from 12.8 to 12.5 hand calculated. On the cluster it says it has improved 2mpg. LOL. So I must have a dirty tune but I can't tell with a DPF. What tools or aids are you guys using to help gauge a clean tune when you can't see the exhaust ?