Welcome to the forum mate.
When I had my d14, I had a full exhaust system, aftermarket air intake with cold air feed, and I swapped the intake manifold for one from a d16z6.
Definitely made a nice difference performance wise but mostly sounded much better.
If I was you I'd do what highland said and improve the suspension an brakes to get the var ready for a bigger engine, as that will be a better use of your money than tryin to squeeze more power from your d14.
Also, I stripped all my interior, as weight is a big factor in acceleration, and handling!
You could also remove air con, power steering, airbags, abs, etc if you have them. Or use lightweight parts such as wheels, seats, carbon bonnet, boot, or other panels.
Plenty of threads already on here on how to do these mods, and what mods to do.
Hope this helps a bit.