As I have been playing with these things for a while I have a few old ones in the bunch too. Two Burns buggies, Two USA-1 Nitro Crushers (one in the box brand new), One Kanai III (with a P-5 and many Hardcore titanium hop-ups), One 777 Special-1 ( with an RB WS7 II).
I am looking to buy a back up engine for the new buggies, don't know if it will be the V-Spec or not. I previously had only OS engines and decided to try something different when I bought my latest buggies. I have heard so many things good about the V-Spec I think it might be the one, of course I haven't tried the Sirio Kanai engines yet.