Hello! I've got a '97 Mack CH613 with the E7 427 (V-Mac II) and 13spd Mack transmission. I've been having an off and on problem with low boost and high EGT for about a year now. The truck has 350,000 original KMS on it (about 220,000 miles) and I'm the second owner. I have owned it for about 5 years now. I use it on my farm to pull a hi-boy hay trailer and to pull a tandem axle grain trailer. The last couple of weeks I have been delivering grain on a 320 mile haul round trip, with about 20 metric tons (44,000 lbs.) On one trip last week the engine wouldn't make much more than mid 20's for boost, when it's usually over 30 lbs. and the pyro was running between 1000 and 1100 degrees Fahrenheit, when it usually never tops 900 degrees. After driving about 55 miles I was able to stop and shut the engine off, and check for any intake/exhaust leaks. None found, grabbed some lunch and fired up again and everything was back to normal, over 30 lbs of boost and exhaust temp. below 900. Made a couple more runs that week and everything was fine. Loaded up and pulled out a couple of days ago and was back to mid 20's for boost and exhaust temperature approaching 1200 on a long hill. Again stopped after 55 miles, had lunch and let the engine cool off. Checked for plumbing leaks, pulled the aircleaner element, removed the aircleaner elbow and spun the turbine: no obvious rough spots or any sticking, put everything back in place. Fired up and delivered that load all the way there and back with low boost and high EGT. Earlier this winter I was coming back from the truck wash and the truck lost all boost and was making some pretty terrible noises while trying to accelerate. Called the Mack techline and was informed that I had probably bent a connecting rod due to "filling the intake with water" or else had a major electronic fault. In a panic I had the truck hauled to Redhead Mack in Lloydminster Saskatchewan the next day. They called me around noon and informed me that the truck was fixed and ready to go. The stealth exhaust brake had failed in the closed position thus closing the exhaust off and not allowing the engine to make any boost. Since parts are no longer available to fix it, they wired the exhaust flap open with some mechanics wire. What has me scratching my head is: why does this problem seem to be intermittent? If there's an air leak, I.E. loose clamp, air compressor feed line worn through, cracked intercooler etc. it should be consistently low boost. NO?? Also if the engine is "de-rating" shouldn't it be cutting fuel which would in turn limit boost AND EGT temperature AND produce low power? The truck doesn't really seem to be short of any power when it's low on boost, but the exhaust temperature is much higher than normal, leading me to believe that it's getting the proper amount of fuel, but not enough air. Lastly, the electronic malfunction light only came on once during this timeline, when the truck was running normal, and empty about 20 miles from home. It shut off when the ignition was turned off and hasn't come on since. Any and all comments/advice welcome! This is getting a little frustrating. I've made an appointment at Redhead for Monday morning, but at $135 an hour, I don't want them taking days and days trouble shooting this thing!! Thanks!! Later, Marc