It maxes out at about 400hp, which in GT3 is not so much.
What more can I do or should I just sell it?

 

don't mess with the spoon...win the STOOK LM Race Car!

 

The Spoon isn't meant to be a killer to all of the cars. Same with the Mugen and the Spoon Race car (There really are two different Spoon S2000s in the game). Race it on some races with lower end cars. It can be a lot of fun. I have all of the S2000s in the game and I made sure I have them all in black (With the exception of the race painted ones.)!