1990 Ford F-150 problems
 

I have a 1990 Ford F-150 I just bought that's not running right. It has the 5.0 motor, manual transmission, and it's the xlt lariat 4x4 short bed. I brought it pretty cheap and it's very clean. The guy that owned before me put a aftermarket Cam in it , short tube headers, aftermarket exhaust with no catalytic converters. The truck runs bad in lower rpms, such as back firing and no power. When I'm on the highway and get into 5th gear it really has no power. As I'm going through the gears once I hit about 1800 rpms it starts running good and has all kinds of power . I called summit racing and they said the cam that was put in the truck doesn't start building power until around 1800 to 2200 rpms . Also noticed that all the emissions stuff under the hood is disconnected. Also uses a lot of gas.
Wanted to know what would be the best fix for making the truck run good. Truck is a everyday driver back and forth to work. Which is two miles each way. Just want to have it run right. I have people telling me to get a aftermarket chip for it, check the timing, and replace everything back to factory . Like I said just want it to run right. Thank you in advance.

sounds to me like the aftermarket cam is affecting the valve timing of the engine

Put it back to stock as soon as possible. Everything, including all the emissions controls. That's the simplest, cheapest, and most-reliable way to get it to run right. Click this & read the caption:

https://www.supermotors.net/getfile/...l/hayneses.jpg
(phone app link)

Pretty common for someone to put a cam in and have no idea what they are doing. If you have it put the stock cam back in, if not look at comp cam get one with operating range that starts at idle. Range will read idle - 6000 rpm or something close to that.