this info should help, btw have someone follow the car or truck in a second car and watch the exhaust from your car,after the engines up to temp while you talk to them on a cell phone, accelerate hard then let off the gas while your still in gear and let the engine compression slow the car truck or motor home, more smoke on acceleration when cylinder pressures high and intake plenum vacuum is low usually means worn rings, more smoke on de-acceleration when cylinder pressures low and intake plenum vacuum is high usually means usually indicates valve seals, and obviously a leak down test adds info
naturally, setting your ignition timing,adjusting your valves correctly, use of a vacuum gauge and pulling trouble codes, and doing a cylinder leak down test and looking for other issues like vacuum leaks,carb or injector problems ,reading the plugs etc, gives more info!
naturally, setting your ignition timing,adjusting your valves correctly, use of a vacuum gauge and pulling trouble codes, and doing a cylinder leak down test and looking for other issues like vacuum leaks,carb or injector problems ,reading the plugs etc, gives more info!