BMW 323 Forum : “increase bhp”

the best way is to install aftermarket cam shaft and do valve train mod's, idunno ur skill level but thats difficult for some if u dont have automotive background.

Well to start off most of the parts off your 325i are not compatiable, but I'm not sure about the intake manifold the OBDI M3 intake manifold if put on a OBDII e36 engine will increse the horse power 20-30. But other then that nothing is compatiable.
As for upgrades to your 323 I would go with performance programing, highflow throttle body, header system to compliment your exhaust(free flow cats are not worth the money). Also look into getting a 3.19 LSD Differental yah it won't increase horse power but it will get all your new power to the ground alot better and make the car handle alot better. Those are just starters to work your way up to something like a cam upgrade as mentioned before but that can be a head ache and ruin your every day driving experience. If you have any more questions about upgrades look at bavarianpower.com and email me their I will be able to help you out further.

you guys forgot about the most important thing, in the 323 it uses the 318 exhaust system, so instead of having a true dual exhaust you have only one pipe.  go to a true dual and hp gains will be significant

Throw a chip in that bitch or if its not a chip type get a power programer

P.S. this car better be a 5 speed or esle I will hunt you down..

What you can do is install a header as well as a chip. The chip is the best bang for the buck. In a 325 i used to have, I just got  a $40 one off of eBay and it made a great improvement in hp, torque, and even gas mileage. The cam shaft is another thing, but much more expensive. If you are looking for more acceleration, then a higher ratio differential would be the way to go, but you will be sacrificing your mileage.
my 2 cents...

it depends how much money u want to spend in it... gruppe M intakes, UUC exhaust, headers will do you for the basic.
then u can get new cam shafts, value train. pulleys. ECU.  
get a light weight flywheel.. that do a lot to help the accaleration..  get new rear diff will help the acc too. but then your top speed will decrease..