1989 mazda b2600i 4x4 problem

I recently bought a 1989 mazda b2600i 4x4 truck. Every since I bought it I've been having trouble with lack of power. The guy I bought the truck from told me it was sluggish until it warms up which is true, but even after it warms up it still has a lack of power. For example you can put the gas petal to the floor and it just sits still. Could this be a timing problem or something else? I don't think it's a fuel system problem, bc it back fires which makes me think it's getting to much fuel or am I mistaking? If somebody could help me with my problem or at least point me in the right direction it would be much appreciated.

Well is could easily be the ECU. Could also be MAF.

Follow the diagnosis page on B2600i.com

Ok thanks will do.