accel is different and sounds completely different

l've got an 89 F-150 that l've had for about two months and its never been able to accel very fast and always sounds like its working pretty hard at 3000 rpm. yesterday while driving down the interstate going at around 3500 rpm, everything changed. l know l shouldn't be trying to speed in this b/c its a low-gear, but it feels like l broke something free and it now accelerates much faster and is quieter. l have no idea what happened and l'm wondering if l did something l shouldn't have or what. if l didn't know better l'd say that l just finally broke my truck in and its working fine now, but l'm questioning if l did break something. any answers would be appreciated.

What engine?

its a 302, at least thats what l was told, and my being new to this stuff, l'm not sure how to check that out for myself. what l do know for certain though is that its a 5L EFI.

Are the brakes working any better or worse since the "incident"? May have had a shoe dragging or the emergency brake not releasing fully. Something I would check out. If it's a 5L then it is a 302ci.

What is the firing order?

something was jamming up the exhaust and it isn't anymore. most likely a busted up catalytic convertor. i've seen this happen a few times