chipping is worth while, but....
You won't get the best out of it unless you fit an induction kit and for full effect a free flow exhaust as well (these improve airflow so you the remap can be effectively used, and also reduce pumping pressure releasing wasted power in your car).
Basically the remap will alter the fuel/air/ignition profile from the bog standard factory one that works across europe (from 92 ron and up) and tweaks it to work with higher (more consistent) quality fuels like we get in the UK (95/98 ron). The autodelta remap on my old 156 was tuned to run on 98 ron and didn't like 95ron as much but that was what I wanted - power/torque & sod the cost.
The general effect is higher in gear speeds (due to the higher revs at the maximum) and a wider power band (she'll pickup from 2.5 rather than 3-3.5Krpm) with a noticeable amount of go (not tons this isn't a turbo - the turbos quote 25-40% petrols 5-8%).
The autodelta remap also does somethign to the selespeed system, improving the response and will also raise the redline 500rpm.
Traditionally parameters can all be tweaked to meet what you want, Id reccomend autodelta or angel tuning from personal & friends experience.
All three together will give you perhaps 15-25bhp but anything else is hard to come by (fast road cams, then you're into super/turbo charger territory).
If your're after stealth cams/chip will be fairly unnoticable, replacing the stock paper filter in the standard box is also worth a little (and improves the pickup even on it's own - I've done this to the GTA).
Autodelta quote improvement figures on their website (www.autodelta.co.uk
) it's about 8 hp depending on car if I remember rightly.
I'd look at changing your insurers that will allow you reasonable mods (chip/zorst/induction) if you feel the need to declare when you renew (try liverpool victoria - I'm happy with them)...