I own a 1990 Honda civic DX with the engine to a 1998 DX... How can I add a little horsepower and or torque without having to spend much money ?

UPDATE>>>> I have alreadyreplaced the full exaust system and addedthe intake pipe... (not sure if it is cold air)

Use full synthetic 5W-30 engine oil (e.g. Mobil 1 or Pennzoil Platinum) and, assuming you have a manual transmission, Amsoil Synthetic Manual Transmission Fluid (MTF).

Yes to all the above, but you also need a session on a rolling road and an ECU remap for additional power output.

The bolt on parts may actually be robbing you of power on a standard ECU mapping.

Its an automatic and I run 5w30 royal purple oil... as far as bolt on parts the only addition is the intake pipe in which I've noticed a better change... As far as the remap goes how expensive of a job is that ?

Since you have an automatic transmission, use Mobil 1 Synthetic Multi-Vehicle ATF. Run Amsoil Synthetic Power Steering Fluid (PSF) in the power steering system. All of this reduces friction.