Hello, hope you can help

The resistance on my bike when going up hills is crazy I have take to a bike shop and had a full service which they did number of things changed BB along with other stuff.

Just checked it out on a ride and it still feels harder than usual on hills, on the flats it seems fine. I'm a serious triathlete and looking at going sub 9hr in Ironman Austria next week but seriously do not have the confidence in my bike now at all.

Example one week I was going up a hill doing 80 rpm and the next going up same hill and doing 50 rpm and that was a massive effort. Today went up a 10% hill and my wattage was 350+watts and my speed was 6 mph this is crazy. God if I would do go that high watts when climbing hills in Austria I would blow up.

This write up is pretty rushed as I'm pushed for time, hope you can help me on what it could be, my thoughts are now going have to get another service when out in Austria spending another £100+ and possibly still doesn't get fixed.