92 4.0 explorer won't accelerate

[CmG]

After a night of "hot rodding" every time I push the gas the engine bogs down and won't shift until way over 3000 rpms. Has very little power under 40 mph but still shifts. I Can NOT accelerate over 50 mph. There is Also a hissing sound that becomes worse when gas pedal is pushed and my gas milage has been cut in half...is it vacuum, fuel, transmission? Any advice would be greatly appreciated

 

[Rick]

Hissing sound sounds like it could be a vacuum leak. I have seen the hose to the power brake booster and the elbow itself rot out.

 

[Josh P]

Welcome to the forum, did the idle change, sound any faster? My van had a vacuum leak from the brake booster.