I'm stumped, car runs horrifyingly bad

[miniz33]

It did this before and after I replaced the fuel pump, dont know if I mentioned that

[tleed]

Have you checked your fuel pressure regulator and if the lights are still flickering check your alternator

[miniz33]

Alternator puts out 13.5 with all accessories on, the regulator is brand new. Car still runs like crap and I'm pulling my hair out over this. Supposed to be able to drag a 5000lb trailer and I have to nearly floor it to climb hills, and no diagnostic pointers at all. I found that theres about six wire splices in the harness over the intake, and a very strange black box about the size of a quarter near it. Anyone ever see this little black box taped to the harness with about four wires coming out of it?

[tleed]

Need to have the alternator load tested just because it puts out the volt does not mean it puts out the amps and could still have a bad diode