Bumpy Hesitant acceleration w/ check engine light on and mystery poof noise..

Hello Everyone.
I have a 1998 Lexus GS 300 w/ 191,000.
I don't know how to exactly describe the problem but here goes.
Check engine light is one w/ p1071 code - too lean condition.
The car idles fine. No stalling. No issues.
The car revs fine w/o issue in park.
When I accelerate, I can accelerate normally as long as I go SLOW.
If I give a lot of gas the car revs for a few seconds, you can hear a POOF sound come from the engine and then it eventually accelerates fast like it's supposed to.
I just changed out spark plugs and changed Valve cover gaskets but this problem existed before that. When I change the spark plugs out, I found them drowned in motor oil. When looking into the holes from where the spark plugs go, a lot of "crud" can be seen.
Anyone have a suggestion or can explain the POOF Sound ??
Much appreciated !
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I also did replace the MAF sensor but issue still exists...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
May be there is some air passing trought aspiration circuit, with a hole opening under pressure.
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.