When cold my '93 suburban dies but once warm runs fine it has a 454 with tbi

Could be bad coolant temp sensor.

Lets start at the beginning. Is the check engine light on ?
You have an idle air control valve which could be sticking open or shorted to ground. You should be able to unplug it to test. There also could be a gasket or hose that is opening up and causing a huge vac leak.

there is problem with relay PGMFI is under left leg.

try the temp sensor by the thermostat housing,make sure its not broken when you unplug it,ohm sensor itself when warmed up,and when cold

for a swap like that a chilton book would cover info for both motors and they cost under 20 bucks. just saying it beats the hell out of guessing at it or taking some schmucks advise from the internet. since your old 5.7 had TBI im hoping the 454 your swapping it with is also a TBI, if not your best bet would probally be to convert to carb but your going to need to replace the fuel system as the 2 high pressure lines that ran the TBI wont work with a carb. if it is TBI your going to need the ECM that came with the 454 as the 350 one is just going to "get confused" and have issues. Since your rig has an older ECM you can remove the Electronic senders and replace them with manual ones to simplify everything ( i have an 89 chevy i built a rat 355 for so ive been through this before) . without knowing exactly the year of the 454 thats about all i can think of to watch out for on that swap, i hope your not trying to mate the 454 to a 4L60, your going to need at least a 4l80 with an upgraded sun shell gear or a heavy duty manual ( at least 10 spline and 12 inch clutch).

Assuming your engine is in good mechanical condition, there are only a few options.

1. You may have a vacuum leak.
2. The pickup in the distributor may be worn to the point that it is sloppy at idle but normal at higher rpm.
3. Idle control valve/motor may not be working properly.

It probably isn't an ignition related problem as the problem would normally get worse as RPM increases. I've seen #2 about 5 times in the past year or 2 so it's not uncommon and would recommend replacing the entire distributor if you come to that conclusion, but would definitely check all vacuum hoses first.

Check the catalitic converter,fuel filter, sparkplugs and sparkplug wires.

sounds like a computer issue on the burb, but i would check the IAC(idle air control) valve and the TPS(throttle position sensor) first.
I would start with the IAC on the 93'.

Check fuel pressure, and regulator. A leaking regulator gives a warm engine more fuel [ it does not like it] a cold motor does. same as a flooded motor. Good luck

There is a valve that allows heated water to flow through the heater core when you select heat on your controls. This valve should be located under the hood and one of your heater hoses should run to it. Your valve is stuck or failed for some reason. Check it out.