why does my mr2 2.2 NA run sluggish after timing belt replaced ?

Just had timing belt replaced it starts smooth idles great but give it
gas and it revs slower feels like it loads up for a second or so then
clears up after about 3000rpm . Slower rev to 5000 rpm  I had to
down shift in places going up hill I would normally up shift and
power up hill to shift again , now it feels like it has half the power it
had...why ?  Thanks for your help