got a diana k 98 mauser in 177 it is the most twangy of twangy things i have ever owned is it worth fitting a tinbum tuning kit or stripping and polishing and regreasing had a quote from cgr who are always very good from 75 to 150 depending on actions taken..bearing in mind it has had about 100 pellets thro it since new last year is it worth doing or not