Practising with metronome beyond strong notes

Doh I know this pops up time after time, but dang.. I post it again :D

I begin to like this site metronome (somehow I feel its changed somehow) Which is actually pretty cool to change the sounds... doh anyway... Ive practised a quite with it now, and I can play strong notes as far to 250 tempo.

I feel pretty confortable playing with 120 tempo that I double the notes... (Quarter notes?), yaeh I lack terminology a little here XD... but reaching say 160 tempo playing 8/4 (I think that is how I should type it)...I found it extremely hard to achieve the speed. Ive tried with pick and without pick.

Ive tried sweep picking...with poor results, its quite messy.. Ive turned to alternative picking and found that more confortable after a lot of practise :), but is it possible to achieve fast speeds like mentioned other ways than sweep picking?

Thanks again
Empirism

tapping? Alt picking is the fastest if you really practice it though.