99 Sonata Hesitation

Not sure how much info to give and still stay brief.
99 Sonata 2.4 4cyl
Bought about 1 year ago. Had check engine light: Code was for bank 1 lean.
Car ran fine. Reset light - stayed out for a day or two.
Several months later performance began deteriorating until car choked out and died
eventually replaced catalytic converter; much improved but some hesitation
hesitation continues especailly when cold; when was car has trouble upshifting
and is especially unresponsive around 2000 rpm
If I floor is it will shift but when I let speed/rpm drop to 2000 or so it wants to bog down.
Someone has suggested O2 sensors.
HELP!!!!
Thanks in advance.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The front O2 sensor is possible, but doubtful. Is the check engine lamp on now? If so, have the code read or a diagnosis done. This code will be the largest hint to the cause of the issue.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.