TR Rob kits came with non standard ID springs which is why your guides won't fit the new one. It's getting coil bound, removing a coil will allow a preload washer, but it'll be self defeating! Maybe try a new piston seal?
New guides would be designed for the spring you now have and fit the latchrod perfectly as that has always been the same size. If it shoots well as it is then leave it, but if you're curious give the new spring a go and see what you think.