96 bonneville needs big time help

i have a 96 bonnevilel se 3.8 liter k engine code. have roughly 158000 miles on it. over x-mas did an upper intake on it. since then i have encountered a lean bank one code (171) i was told by the dealership that my front bank of injectors were bad. i recently (as in monday) had enough money to buy the 3 injectors and replaced them. it then through a 300 muliple random misfire code at me. since i have installed the new injectors i have changed the fuel filter, new ac delco iriduim plugs, new ac delco wires, three new coil packs which seemed to take care of the 300 code for a few hours, i have also installed a new coolant temp switch. still throwing the 2 codes and it runs real rough on cold start but once it is running it seems to be fine. also seems to hesitate really bad almost liek it is going to die. i had a new ac delco fuel installed about 2 years ago i am learning towards a tps senor now that i have replaced the coolant temp sensor. a few people have suggested the module the packs sit on and also a fuel pressure reg. and even a new o2 senor. the front o2 sensor is about 6 months old since i was told that was the problem by a shop and replaced it. any ideas? any help would be great. thanks

update: i have now replaced the map sensor, the tps sensor and the ful pressure reg. i am about to replace the o2 sensor and the module. any ideas?

what about the spark plugs and wires? The plugs could be fouled due to the bad injectors or maybe the wires aren't fully engaged on the coil towers.

Just an idea,have you checked the fuel pressure with a gauge?I've seen other cars where even though the fuel pump ran
it didn't make enough pressure causing the car to run like crap and occasionally die. I can't see three injectors all going bad at once all on the same fuel rail.But I can see them not operating together because they are linked together.

as for the wires and plus i replaced them right after i replaced the injectors because i thought the same thing that running lean for a while had killed them.
as for this idea about the fuel pump not having enough pressure, this si interesting since i had the fuel pump replaced about 1.5- 2 years ago and i am starting to wonder about it but my only question is them problem seems to only be when the car is cold could this still be an issue?
thanks so much for all the input this si truely great because ia m stumped and don't knwo where to go next