2000 Toyota Sienna Car not accelerating

It was misfiring for several weeks that is why I tried to change the plugs. I changed out the front 3 and it was running much better, until I tried to change the rear plugs.
I was able to get one rear coil out, but couldn't get the plug out, so I put everything back together until I had time to complete the job. Now it doesn't accelerate at all until it warms up. However even when warm it idles rough, runs very choppy, and will sometimes hesitate when trying to accelerate both on the highway and from a dead stop.
Thanks!

Yes the check engine light did come on and it does seem to be misfiring more than before. Perhaps when I took the back coil wire off, I didn't reattach it properly. I think I need to finish the job of changing the plugs. The coils packs are very expensive on the sienna's, any way to check which ones are misfiring?

Thanks! Big help!

My van recenty started losing power when I press on the accelerator. When driving, the speedometer will drop down to 0 then a few seconds later jump up to 50, then fall back down to 0. It is like the van is confused and doesn't know if it is going or not. After losing power, it will all of a sudden accelerate back up to the speed I was going. The ABS light, flat tire light, check engine ight, and brake light are all on. Only the left half of the dash lights are lit. Have already taken in 1 time to be checked. They unplugged and cleaned everything. It helped for a couple of days. This is the second time to take into the shop.