Well, I guess it's time for me to chip in. When I first start to modify the GVR4 back in 92 there wasn't anything available except the PFC-FCON and VPC. VPC for Eclipse GSX and PFC-Fcon for Gvr4. I feel that Eclipse and Gvr4 is close enough that I tried the VPC for my VR4. I tell you what, IT WAS THE BIGGEST/Most Expensive piece of sh*t tunning tool I have ever wasted my money on. Never run right, always hiccuping or bogging or jerking when tip in throttle, I HATE THAT HKS sh*t!!!! Yeah, did I mention the time I put into make it work??! over 3 years with it and nothing but problems not to mention the constant jerking causing constant shock to my driveline that caused me even more problems and money! Yes, the second I got it off the car, 100x better! This was back then, without much options, but now... you have so much! pick anyone and it will work better.