Need more power

[4subaru]

I have a stock 2.2 N/A in my 90. I have a lightweight crank pully and thats it, i plan on sending my cams to delta for a regrind, but i would still like a little more out of it. I would perfer not to be swapping heads or pulling the motor and completely rebuilding it. Is there anything else that is more or less bolt on that increases power without spending over $500?

[Murphy]

Borla makes unequal headers for the 2.5Ls but they fit without problems, but i think the exhaust comes out on the wrong side of the car, but thats easily fixed
its like $385
i think it was Cobb that used to make equal lengths but i cant find them on the site anymore, might have stoped making them

[206er]

naws

[4subaru]

I see some people that were using the MSD DIS, are those worth the money? What all do I need in order to install this?