Alias, where are you located? There are probably a handful of people on this forum in the same area that could give you advice on fast-but-not-Cat 1-fast groups to ride with. The best workout I get besides races is when I force myself to hang on to groups that are faster than me. Looking at numbers and pushing yourself solo is well and good, but at some point most of us lose a little motivation and go a little soft. Trying to hold the wheel of someone much faster than you with the knowledge that losing the wheel means you're dropped, solo, in the middle of nowhere is one thing that forces you to dig deep.