Hot Rod had a article on a Mopar P5 I-4 engine that made over 800hp on a dyno, and said that on 35 psi should have no problem making over 1000hp.
The article was about the BlowFish 2nd Gen Barracuda....and setting the top speed record for that engine.
Sick!
http://www.hotrod.com/featuredvehicles/113_0702_1969_barracuda/photo_16.html