Sounds like you replaced some obvious parts to me but have you thought of switching out the TPS (throttle position sensor). That would have been my 1st choice unless a scanner was telling you different.
You might want to post an introduction in the Welcome Mat fourm. I think folks would be more likely to reply to your post if they knew that it was enthusiastic newbie fourm member rather than just a random solicitation for advice.
An afterthought... Some times it helps to clean throttle bodies out. I think Scotty Kilmer or Chris Fix both have helpful videos on YouTube for this. If this was a carbuerator I'd say start looking for vaccum leaks around gaskets, etc... Has this 454 ever been seriously overheated? What's the mileage and PO history? A little background would help to.