About how much added horsepower would this generate?

I own a 1998 Honda prelude automatic transmission and I want to put some money into the cars performance. I will be adding a cold air intake, cat back exaust, high flow catalyst, and re flashing the cpu to tune the car. Overall, I was hoping to get close to 30 hp or better from these mods. I would love to add a turbo but I don't have the money for "the good kind" and I'm not interested in blowing up my engine. A horsepower estimate would be nice and any advice on other upgrades to buy would also be appreciated.

No more than 10 you would need to more mods than that like higher compression pistons, a better valve train, and jdm stickers.

1 Horsepower is under 20, 30, Not even close. Those mods/upgrades lets your engine breath easier, cold air intake - for breathing in, cat back and high flow catalyst for breathing out.

You'll improved throttle response, so slight improvement in acceleration not to be mistaken as horsepower gain.

Tuning a car right makes it run efficient, you don't gain any additional horsepower.

Now if you do add turbo, then there's an increase in the compression ratio which increases the horsepower output. And a turbo will only be efficient with those upgrades installed.

Sorry kid, you aren't going to get anywhere near 30hp from those simple mods. Here's some fun.
A 1997 Prelude SE with the H23A1, in a prominent Import performance magazine was dyno tested with some modifications, here's the results.
They first baselined it with no mods. It made 122.1whp and 124.8wtq.
They first added an AEM cold air intake. This added 2.8whp and 3.1wtq.
Next they added a Skunk2 Exhaust. On top of the intake, they gained 5.3whp and 2.5wtq.
Finally they installed a DC Sports 4-2-1 Header. That gave an additional 3.9whp and 4.8wtq.

All told, an intake, header and exhaust cost them $1300 and gained 12whp and 10ft-lb torque. That's nowhere near 30hp.

Even if you add tuning on top of that, you won't gain more than another 3-5whp on a basically stock engine.

Let's put it this way. On another Prelude in that same magazien, they swapped out the entire valvetrain for aftermarket camshafts and only gained 7.9whp, but lost 11ft-lb torque. So they made the car slower. You aren't going to gain 30hp from bolt ons, you will have to get into the engine.

With the mods you mentioned I'm thinking under 20hp.

In other words anonymousgearhead, don't waste your money question-asker. Great citation BTW.

Not sure why import "tuners" think their "mods" do anything, basic physics will dictate that not changing the ability of the engine to breathe (camshaft and heads) will not result in meaningful power gains. $1300 for 12HP? Talk about a waste of time, that's a new set of heads!

They won't add much torque.
But custom exhaust will make your car sound cool.
A performance chip can really help.
Check out here http://www.carid.com/1998-honda-prelude-performance-chips/

If tuned right minimum 30hp. Max 50:D