1999 Gmc Suburban no power after half throttle have to start vehicle with starting fl

[MrOrange]

So i have an issue with my 1999 suburban that is hard to get an answer on

So the burb has had this issue since ive owned it
I have to use starting fluid to start it when its cold
it has no power when accelerating past 30%
backfires back thru the exhaust

so far i have replaced the following parts

used intake assembly off of a running 5.7l
new direct fit cat and new 02s
new fuel pump , not sure if filter also was?
good working , maf , air temp sensor and igniter.

im thinking the engine is running to lean or too rich which would explain the no start with out starting fluid (lean) , or the engine is running too rich and backfiring thru the throttle body . not sure if ineed to replace the spiders or not?