Need help with fuel problem.
 

I have purchased what appeared to be mainly stock 88 5.0 5 speed coupe last October. The car is still speed density and has the following mods on it

Underdrives
K & N in box filter
Mac Shorties, Power Box and Pro Dumps
Taylor Custom fit 8mm wires

Parts replaced:
Map Sensor
Plugs
Oxygen Sensors

My problem #1,

I am flooding out at idle and backfiring badly. I have 55 lbs of fuel pressure at the rail at idle and a factory fuel regulator. Will it help to replace the regulator with an adjustable one to drop the pressure down. Where else should I look to fix this problem.

Problem # 2,
No check engine light a mechanic friend of mine said some cars will not run without the light being active any ideals on how to fix it?

First of all with a near to stock 5.0 you can run 38psi 50+ is way to much. To answer your second question on my 87 mustang i have the spot for the check engine light but it never turns on

later

That fuel pressure is WAY too high and is probably the sole reason your running bad. Probably a fialed regulator - put a new one one and adjust to 38-40 as mentioned.