Got my car dyno-tuned(powerfc) by Guilt-Toy around 2months ago, retune and touchup from 100octane -> 98octane. Even with the lower octane rating the car is making around 20rwkw MORE! on Guilt-Toy's dyno and reconfirmed when i ran my car at the SAU Dyno day and made 245rwkw where on my previous tune only made 225rwkw.
He spent a good 2-3 hours on the tune mainly targeting the low end which my previous tuner didn't even touch, so now it doesn't blow a cloud of black smoke when i floor it and is alot smoother.
Also got my O2 Sensor changed with the help of Guilt-toy prior to the tune and because it wasn't coming off, we had to drop the dump pipe to change it.
My fuel economy is up especially for freeways but even for city driving, power is also up! what more can you want?
I'm very happy with the work done by Guilt-Toy and the attention to detail that he puts into his work, and can recommend him to anyone that requires their skyline tuned.