For me, the LRP28S3 was plenty for the savage X. Odds are, the 25 will be too. If/when my LRP28 in my big block revo dies, I'll more than likely go with the LRP21 to get a few more RPM's and more controllable power.
I think that screw at the base of the carb neck is for a boost bottle...
Well, as the old adage goes... you get what you pay for. If I were you, I'd just save up for the LRP32. I've been in the hobby for nearly 20 years. For the first 5 years or so, I dealt with cheap budget engines. At the time, there were many. Then I got my first $200 engine, OS18TM for my revo. A...