this is the best way to learn about your car
and now only have the lean codes is a good thing...once you throw mis-fire codes in there as well, it's as though they're telling you two different things
as for the intake hose...it is most likely not your problem anyway, since on the gen4s/solaras, the MAF is pretty close to the throttlebody, so the readings won't be thrown off much even if it's right above it.
in regards to what to troubleshoot- clean your MAF first, and if you have another fellow solara owner nearby, swap MAFs and see...
ignition and sparkplugs you can leave, since if they are not working properly, you'd get the misfire codes again and run rich, not lean.
you can take out your injectors and get them flow-tested- BUT since you're getting both front AND rear bank codes, then chances are that it's not the injectors. I would actually check to see the working condition of your FPR by attaching a fuel pressure gauge.
Also, you don't list an upgraded fuel pump on your mod list. do you have one?