Motor help
 

Ok guys I need some help. I have a 29 foot Warlock WC. I got it in a trade for my sand rail. Took it to the lake a few weeks ago and it did ok. At WOT I had it up to 60 MPH at 4400 RPM. Had the Carb rebuilt and took it to the lake again. Now I only get 55 at WOT. When it 4700 rpm it starts popping and snorting like it running out of fuel. . The guy I got it from is saying that it a 1998 454 block with a 496 cam. It also has a B & M 144 blower. I have a few questions

1. What is the Max RPM on the motor
2. How fast should this boat go? 454 with a bravo 1 out drive.
3. Why does it fall on its face at 4700 RPM

You either have an vacuum leak or the float level has changed from it's original setting.