Engine runs rough after oil change

[Q45]

The car is an 1991 Infinity Q45.
It seems that just changing the oil should not make it run considerable worse but here is what I did.
I switched from standard oil to synthetic 5-40 (Chevron Delo 400).
I emptied the old oil and filter out and then ran some cheap 10-40 chevron oil through to rinse it. I then put on the new filter and added the Chevron Synthetic 5-40. It was immediately hard to start (cranked a lot before starting) and ran rough at certain speeds. Everything I know about cars says this isn't possible. I did have to take the switch off the aircleaner to remove the air cleaner because they hide the filter beneath it but I put it back on....so I am scratching my head on this one. Does anyone have any ideas?
Thanks

 

[Vspec]

Because you played with the intake system, i would double check that first, oil can't make a car ruin that much worse IMO.

 

[Q45]

Wow that was fast.. I will check that out. Thanks!

 

[qship1996]

never try to change filter on a q45 from above,always from below after removing the underbelly sheild. the mass airflow sensor you unplugged on the airbox is a fragile item on q45`s- go to www.nicoclub.com to learn all about q ownership,and have fun doing so!

 

[Q45]

I must have done something to the plug. Boy those filters are hard to get to..Thanks for the input and the link, I appreciate it.

 

[mechtech]

Right. You probably knocked something loose when changing the oil.