Ok, knowing you have a 5-pin, and it gives the other person a silent carrier, tells me that this is more of a modulation issue. So the Mic amp itself is "current starved".
If you've removed R131 (148GTL) - might want to put that back in - work another section to help with the dropout.
Go back to this thread ...
https://www.worldwidedx.com/threads/volting-a-cobra-148-gtl-final.100144/page-3#post-761237
The post you need to review - if modulation is all you want - then start there - my response is below that one in the thread.
I'm not telling you to volt a final - far from it, I'm trying to offer you clues as to what you can do to help with your losses.
If you're like me, I get pissed when I look at my energy bill, wondering where all those watts actually went - were they wasted or used or stolen?
If that is how you feel, then take charge - meaning your radios' power supply has something stealing power, it's glory - from you, when you use it and it can't keep up...
Start cutting down the power drains...
Heavy saturated modulation - draws down power - it has to get it from somewhere, so if it takes too much thru a constriction - the voltage drop is too great and in stock form - the mic amp uses the MB3756s' constant supply regulation rail - too many branches on the tree asking for power - the tree cannot, simply cannot, keep up.
Start by reviewing your operation - does your power supply; linear or switching - is it able to keep afloat? Ever run a DVM in Voltage, hooked up across the output of and watching - monitoring - the bridge rectifiers' performance - in DC and AC? You might be surprised to find problems in the power supply you didn't know about by looking at both the DC realm, and the ripple side - by looking at the AC voltage too.
Some linear power supplies can benefit from a capacitor overhaul - the addition of a large value (1,000uF or even 470uF) can help smooth the ripple - obtaining energy in storage thru the extra capacitance - to lessen the regulation and sag / draw down - that does occur in a linear power supply - the current demand places the pass transistor in linear region forcing a dropping of voltage across it generating heat - some of this can be avoided if the ripple effect was less - by increasing the reserve voltage to a certain degree - to help sustain the voltage for a longer period of time before the lag and drop occurs. Adding capacitance before and after the regulation circuit can aid you in keeping enough charge to handle the occasional drop in power due to demands.
Volume control - a long abused part of the chain - contains your on-off or maybe thru a separate switch - but the switch part - carries the ENTIRE radio load across the terminals of itself and any long term arcing issues or neglect - will rear it's head here too.
If you've had work done or recaps - and if the MB3756 cap hasn't been changed or they used a different value - that can cause a dropout in regulation, simply a performance issue.
Have you checked the mA draw of the Driver and Final as of recent? Recheck if you can - higher mA draw had to arrive from somewhere, that is from the MB3756, not a simple power feed from the On / Off switch.
The PLL section runs a Tripler - takes it's toll on parts - might want to look into power filter caps - not just the Electrolytic - the Disc caps here too. Age and power surges take their toll of power supply buss feed filtering caps - they decrease their effects (ESC) as they age and begin to look like resistors (ESR).
If you try to make the Audio Chip "sing" a stronger tune, that too can cause the dropout - changing the AM regulator also does this - the latter technology realm has better performing transistors - so they can keep up with todays digital demands. Yes I said digital - it may be your correctly numbered part, but if it's not the STOCK or even if it is - what else are supplanting into the radio to affect the chain - does have long term effects.
If you've changed or have had work done or haven't had it looked at in a while - better talk to the tech because the work they did is causing you to clip, or you have work that needs to be done to keep it going.