E46 320i performance

Firstly, welcome!

There are a huge number of options here.

It's difficult to say they'll directly benefit 1st and 2nd gear more than anything though, but there are plenty of changes that would benefit the car overall in terms of performance.

For example (and this is just a few):

Basic ECU upgrade (Superchips etc) - 10bhp, £300

DMS Automotive will do higher ECU upgrades £500+ than can add much more bhp but you'll pay in terms of driveability too.

Supersprint manufacture an exhaust system that, depending on whether you go for front, middle, back etc will give anything between 5-12 bhp increase

Air filter changes from the likes of Piper Cross and K&N will give you between 6-12 bhp and are cheap on the scale of things

Whatever you do though, you're not going to get huge increases in performance unless you spend upwards of £1k and you can go to £3k and much more if you start looking at Turbo's, Superchargers etc ect

ello and welcome

i agree with coasting .hes hit the nail on the head and couldnt have typed it any better.theres loads of things out there its just a case of .ya pays ya £££ you take ya chance... apart from going to 330 status .its up to you .however if you do the re chip and filter .you mite be able to keep up with the old e36 2.5 motor .thats on standard tune .gaining 300 cubes for the small price of the filter and re chip is small fry .go on you wont regret the spend