Most anyone on this forum in need of HP gain should consider flashing their ECU with new software. I see many sites now offering roughly 20/25 hp by updating the ECU by way of a laptop flash program. hooah Looks like the price can ranch from $425 to $1,000, plus S&H.

But if you don't have any money to spend on your X car let me offer a few back yard tricks.

(a) If you can get your cooling fan to cut on sooner and keep the engine cool you'll gain more HP by way of the ECU advancing engine timing.
(b) Run the highest octane fuel you can buy, that way the engine does not ping and the ECU will allow more advance timing.
(d) Replace your air filters with high volume air flow filters, such as K&N High Performance Air Filters.
(e) Turn off your traction control so your engine is more responsive coming off the red light, may not be HP increase but you ECU feels better about allowing your engine to suck in more fuel.
(f) This one here I'm not real sure about, we use to do it back in the old days, and it may be more trouble then it is worth. Rig up a can under the hood and feed your fuel line through it, then pack it with ice when you are ready to gain a horse or two. The ice keeps the fuel cooler as it enters your engine and therefore you get a better burn and power increase.

The best I can tell with the automobiles of today is this: Keep the engine cool, high octane, and timing advance. It's all about tricking the ECU. hooah