scooby_nd67

I've got a Type R Version 5. I have followed with keen interest the topics on the Version 5 being "sensitive" to the octane level in the fuel.

There are 2 types of ULG available domestically - Premium RON 97 and Super RON 92 Unleaded. I have always used the former since day 1. In addition, I used an octane booster (called Nulon from Australia) to increase the octane level in the hope that it'll match the Japanese 100 RON.

So far I haven't had any problem with the engine losing any power. The car is not idling properly and this is more apparent since changed to a 3" HKS Hiper exhaust).

I have had the garage check out the exhaust couplings/joints for any leaks, spark plugs/cables but the car is still misfiring. The problem is that the engine idles at circa 500-650rpm and 800-850rpm (with A/C). Isn't this too low?

The problem with STIs in my country is that the dealer could not furnish us with a manual/handbook in English.

I haven't had any ECU/filter/blow-off valve or any other upgrades save for the exhaust.

The garage told me that they suspect a leak in the piston/cylinder. This is to be confirmed when I have the car checked out using the computer diagnostic compression thingy later this week.

My question is whether there is still a possibility of so-called melted pistons problem even when I'm running on RON 97 with octane booster? How can I overcome this problem? Will an ECU remap/upgrade be the solution?