aftermarket TB's generally have idle issues. If you have the stock TB....might want to put that back on to see if your issue goes away.
A scan tool that reads IAC counts will help. If they are pegged at 160, especially when your idle does drop, you need to do one of two "fix" methods to the 58 mm. This requires a scan tool to read IAC counts as you mod the 58 mm. You either drill a hole where the stock one has one or crack the TB blades open and then drill/slot the TPS housing. The later I don't endorse but people have done it that way. Do not blindly do either without having the ability to scan/read IAC counts
IAC counts want to be 30-35 (32) at idle with engine at operating temp. TPS volts want to be .67 vdc blades closed and 4.5 vdc full open. volts should increase evenly and smoothly when you open the TB blades
also after you start the car and it runs for a moment, shut off, and then pull the rubber elbow from back of FPR....is there any sign of fuel in it? if yes FPR is bad....although not really why idle issue is FU. More the fuel smell you have and hard 1st start attempt.