The HP~Ft/Lbs was certified http://archives.media.gm.com/us/powe...0LD8%20DTS.pdf
And people often misquote the certified specs for the L37, it was not the rounded 300. http://archives.media.gm.com/us/powe...0L37%20DTS.pdf
It was 292HP@288Ft/Lbs
The LD8 motor'* tuning profile wasn't actually "de-tuned" It was altered to provide slightly more torque then the L37. One of many cases of "it isn't the HP.... but what is done to deliver the most torque out of HP. A physics item hard to explain or rationalize to numbers oriented people. But the simple fact is more torque, faster car. A LD8 has an advantage over the L37 torque-wise and I've read that was the reason Pontiac'* concept team went with it. Same price point really to them.
To bad they couldn't have swallowed some warranty worry and used the LD8'* brother the LH2. Same engine with 10.5 to 1 compression (LD8 10 to 1) That half point takes the 4.6L to 320 hp @ 315 Ft/Lbs. A bit more than the GM Engineering'* 305 max for the pricey (in Pontiac terms) 4T80e tranny.
I just state both numbers when people ask and sometimes add "up to 350ish HP" with spraying. I really don't use the nitrous much anymore and even though my kit has 75-100-150 HP add nozzles; the engine has stumbled on the 100 HP nozzles and caused me to back down.
The whole thing really doesn't bother me. I bought the car new and if I wanted sheer numbers/performance there was a nice black on black GTO sitting next to it with solid numbers. For less money. I bought the car because of it'* room, style, and comfort along with a nice smooth Northstar. Unique to Pontiac as well as the GXP badging. Coming into this forum 5+ years ago gave me a Mod bite but it has faded. Still happy with my purchase and never looked back at the GTO. If I wanted a nice looking track car, it can be found for half the tradein value of what I now own. But it would not have the things that attracted me to the GXP in the first place. If I wanted raw muscle, with 30k cash in my hand, I wouldn't have been shopping at Pontiac in the 2000'*.