Aftermarket fuel tank issues
I recently got a 97' F350, this truck has a aftermarket 40gal fuel tank (image shown), the other day I was on the highway and it really struggled to go 70 and ended up bogging down and shutting of as I got on the off ramp, after I got home from I was checking fluids to trying to troubleshoot what had gone wrong as I was checking the transmission fluid I gave a knock on the aftermarket tank and it sounded Hollow and empty (fuel Gage broken) witch was weird because I had been driving on it for a few days, but never got above 40. So my assumption was the front tank was pulling fuel from the rear tank then feeding it to the engine, but as I got up to higher speeds there wasn't enough fuel pressure and it died on the highway but ran fine on the way home on rural roads. The next day I filled up the rear tank because I noticed that it had lost fuel since the last time I filled it, that further added to my assumption, I also added fuel to the front tank but for some reason it topped out at 20 gallons even though it's a 40 gallon tank. I then switched back to the front fuel tank and went on the highway and it seemed to run fine (I also test the rear tank and that ran fine as well) after I got home I sat in it and let it run idle for about an hour on the front tank, during that time it started to rev a little weird and then was about to die on me then I switch to the rear tank and it ran normal again. I then got out knocked on the front tank and it sounded empty. This is where I'm at right now I'm so confused on this front tank situation but the rear tank seems to be going just fine. If anyone has any idea of what could be going on that would be much appreciated.