According to PTG doing a full blueprint and converting to a Motec Alpha-N engine management system gains about 45 HP, so a chip alone is not going to get your 20 - 30 HP.
More like 8- 10 if you are lucky. There is NOT a lot of extra HP available in these engines by simple means.
'95 Alpine M3 LTW
'00 Dakar M Roadster
'02 Topaz M3
Red/White SRF #4 (Chassis 561)