This question gets asked more times than I care to mention on the Neon mailing list and Info Exchange. Most DOHC Neons make 114-115hp at the wheels and SOHC Neons make 109-110hp at the wheels stock. Neons generally weigh (5 speed versions) 2400-2600lbs (base model coupe to fully loaded Sport model). Below you'll find the dynojet results from a DOHC ACR coupe and a SOHC ACR sedan. Both are '97 models. Note that '95 model SOHC Neons had a "stronger" camshaft installed.
Stock DOHC
Stock SOHC
The intake system is the best place to start on ALL Neons. The factory intake suffers from heat soak and is rescritive at best. The first generation intake featured a 3" flared tube sticking out of the air box. All Neon intakes have the air box placed over the exhaust manifold. The second generation intakes moved the coil pack lower so that a "scoop" can be placed over the valve cover. This change was made because of non-enthusiasts complained of too much "intake noise". The result is a much more quieter intake system and no lose in overall power. For those on a budget, you should look into replacing the stock paper filter with one from the list I have here:
These filters outflow the best paper filter by a large margin. This should give you a 2-4hp gain overall by increasing and straighting out the flow of air into the engine. Cost $25-$40
For those with a little more money can next remove the intake system all together and get one of these intakes listed here:
Quikpipe dynojet results
These are a good upgrade from the stock intake and air box. They not only improve engine, but save some weight also. The Quickpipe has been dyno-tested to increase power on Neons from 7-10hp on either engine. The NemoAir/Kirk should have about the same results. Cost $104-120
I saved the best for last. Cold-Air intakes make more hp than any other intake system listed here. Expect a 10-15hp gain from either the ICEMAN or AEM intakes. If you want the best upgrade for your Neon, then start here! For more info please click on Cold Air Intakes
Your next upgrade, exhaust will give you the biggest gain after changing your intake. Exhaust mods don't seem to work so well for the DOHC engine as the gains from changing the muffler has resulted in minmial at best. I would only consider changing the muffler on a DOHC engine, only if you have gone beyond the bolt-on stage(ie: headwork, nitrous, etc). For SOHC owners, like me you can pick-up an easy 8-10hp from just changing the muffler. Neons are blessed with 2.25 inch mandrel bent exhaust systems from the factory. So the muffler is the main resriction on the SOHC and less so on the DOHC engine. This is because the SOHC engine is the standard engine available in the Neon. For those without alot of money to spend, you can go two ways. Get a DOHC muffler or get an aftermarket muffler/exhaust system. The DOHC muffler will result in about a 3-5hp increase over stock. These can be purchased from the dealer new, but with prices over $200, it's better to get a aftermarket muffler or exhaust system. On SOHC you can gain from 8-12hp. I gained 8-9hp over the factory DOHC muffler on my SOHC Neon with the Thermal R&D exhaust system. You can expect close to the same results from any of the exhaust out there. To find out more about the exhaust systems available click here.
For those that just want a simple muffler change, I would suggest a Dynomax Ultra-Flo muffler or some other high flow, straight-though muffler. You'll get the same gains without the tips or the "flash". Cost $50-280
Are you ready for Stage 2? Click here