It's a tough question, it also depends on which Evo model are you buying and the selling price too.
and insurance for RM160,000 insured value would cost you around close to RM4,000 without NCB.
normal service (oil and oil filter change) would cost you RM300 (if motul 300v) but if use other full syn oil will cost about less than RM200. i usually service my car after 3000km but some mech would say 5000km is ok; hence its up to you when to service, i would recommend servicing frequently if u do make your baby work hard.
major service (all gears oil - AYC, ACD, Gearbox + normal service) will cost around RM1k. This does not include changing belts.
if you don't mod your car much then the above would be a good idea on how much will it cost to maintain your car per month.
the above is based on my evo7 and i am not sure if it applies to earlier/later models.
IMHO - if it's a used car, more than 3 to 4 years old, i would advise leaving a side RM500/month for normal service and replacement of wear & tear parts. So do budget in extra RM500 to your monthly installment; eg. RM2.5k (installment) + RM500 = RM3k.
hope the above helps.