I have a 1999 F250 with a 7.3. I run a superchips 6000lb tow program in it right now. A few months back I ended up with the the injector plug problem. One bank wasn't firing. I made the little shim for the plug lock and fixed it. Started it up it runs again. Since then I have noticed that it doesn't have the power it used to. I thought maybe I had put the stock program in while diagnosing what was wrong with it so I reloaded it. That wasn't the problem. It used to pull hard up over 1200rpm now it's kind of flat like the stock program I don't see any black smoke come out of it anymore when I put the throttle to the floor. Also just took it on a trip and it does not want to go more then about 82 mph unless it was on a down hill. And it takes its time getting there. I have driven this truck 95mph to 100mph no problem. I could tow my enclosed 24' trailer up the hill 70mph and down the hill 70mph. I have gone over everything I had apart and it is all back together properly. Initially I thought maybe I didn't get the turbo pipe back on all the way but all appears well. I'd don't know if this is just coincidental or if I could have disturbed something. In any case if anyone on here has any input it is appreciated. Tks!

 

Are you getting any boost? Got fuel pressure?

 

Yes but I don't know what the psi readings are yet. I have no gauges I the truck.

 

What should fuel pressure be? What kind of boost should I look for at 1200 rpm and above? I will get some gauges on it.

 

In general I am wondering if this is something anyone else has run into

 

by chance did you update your Superchips programmer thinking it might have been the problem. If you did, that's where your power went. Superchips had to change their programs because they were not EPA compliant (too much black smoke). I had it done to me on my 05 6.0.
When I first got the programmer, it would bark the rear tires shifting into second gear. The truck run it's *** off.
After going on line and doing the update, the truck did not ever run as good.
I bought mine from Pep Boys. So I returned it as being defective (told them it made my trans slip) and got another and never updated it again.

Just thinking.......

 

That's great thought and thanks for mentioning it. Now I know not to do that. I haven't done anything other than take the program in and out of the truck over the years. I am open to any thoughts though. I'm not thinking of something here. I have to find some time to get it back in the shop and look to see what could be going on. Thanks!!