get a good quality impact driver.It will loosen the bolts that are tight.You will also need good torx and hex bits for on the impact driver.That's how I get all the tight stuff loose on my bike and the wifes bike.
ifs a Allen bolt use a Allen head socket with a breaker bar. the longer the bar the easier it will be tobreak loose. (may have to use an extension on end of breaker bar)
Hit the end of them with a propane torch (thin, low flame) for a few seconds and they will come right out. I've used this many times on various stubborn bolts and it works everytime.