whats the diffence between 3.4 and 3.4 H.O.

[don]

you see some grand am's on the road and some say 3.4 H.O. what makes it a high out put?

[BlackJack]

Some of the Ram Air models were badged H.O. and have a 5hp increase over the standard Grand Am GT models, but the engine itself is actually the same LA1. There is some speculation and argument over slight tuning differences, but I seriously doubt it.