I often read about how crappy the chrysler TBI system is. I've a 1989 b250, for 20+ years and 100K+ miles now, and just drove it cross country, or I would have responded sooner.
i don;t want to Taunt Murphy, but
The only surging issues I had, was when I had a failing fuel injector, which is about a 2 minute job to replace and a new injector is under 50$. It is pretty easy to see feel and hear the difference in a malfunctioning fuel injector with the air cleaner cover off. can swap the injectors to see if the problem follows the injector or its wiring
I have had issues with the engine computer. The original likely failed because of a wire to transmission overdrive solenoid was shorting to ground. The replacement ECM was damaged about 12 years later, by the weight of the wire bundles of the 14 wire connector hanging on the solder joints of the 14 pins. I removed the potting, reflowed the solder, and no more issues. I also remove the weight of that wire bundle from potentially stressing the circuit board's pins. Turn the Key to On, not start, and gently apply different pressure to the 14 pin connector. if you hear a relay or relays click on and off it is likely that this is now, or will soon be an issue.
Get some Caig DeOxit d5, no other electrical contact cleaner comes remotely close, but they are useful for helping to flush out old crusty dielectric grease, as the Caig is too expensive for this task.
Do ALL the sensor connectors, MAP and TPS. 02 sensor, coolant temp sensor as well as at the ECM. Every connector you can find. open it flush out old dielectric grease with CRC QED and bottle brushes, then Caig Deoxit.
Flush the connectors of old dielectric grease with CRC QED or similar, and some dental style bottle brushes, then use the Caig Deoxit and the same brushes. Some small precision swabs soaked with deOxit afterwards on the pins, will likely turn black and the pins go from grey and dull to gleaming like silver. https://www.amazon.com/Tamiya-Cotto...mp;psc=1&refRID=326PHGWF1QMFFS6JMPKB
The sensors get sent only 5v and the engine computer sees a returning voltage on these connectors and determines fuel air ratio and spark timing, so highly resistive connections from corrosion on a 32 year old vehicle can have huge effects on driveability, MPG and power. the lower the voltaeg the more affected they are to electrical resistance. Doing all my sensors alone made it feel like I removed 500+ Lbs from the back of my van. Throttle feel/driveability improved dramatically just cleaning the sensor connectors.
Do NOT be one of those people, who opens an electrical connector, sees dielectric grease, and assumes all is fine within and reconnects it I've had di electric grease peel off pins and sockets like 30 year old scotch tape, after removing all the grease which appeared fine and dandy surrounding it.
The engine computer gets its ground, from the intake manifold where the ignition coil attaches. Make sure this is clean and tight. Follow the original battery to engine ground, remove file/wire brush shiny spray with deoxit d5 and retighten. Follow the smaller wires to from battery negative to firewall, behind battery. Same treatment.
It is a good idea to ground the frame to the Engine as well. Best would be the same bolt as the Battery to engine ground, and best if this is a bolt holding the alternator bracket.
The ONLY way I would consider a carburetor swap is if I could not get a new ECM or the parts to repair mine, AND I was not concerned with either fuel economy or having to pass emissions tests.
if driveability conditions happen only with low levels of fuel in the tank, it is likely the fuel pump is on its way out, but do check the connector and the frame ground for the pump at the cross member at the fuel tank. Same CRC QED then Caig Deoxit treatment here. The lower the voltage reaching teh fuel pump the hotter and harder it hat to run to supply the fuel needed, so a shitty electrical connection here can induce premature fuel pump failure. the wiring gauge and the extreme length of it that chrysler used is also pretty inadequate even for the 4 amp load of the fuel pump. I bypassed around 10 feet of it as it actually runs up and over the upper frame rail over the back doors stock. I think the power for the Fuel pump is a green wire with red stripe, 16 or 18 AWG. It gets ground from the nearby cross member. This is where the additional frame to engine ground can be beneficial.
One last thing, is the cabling at teh battery itself. often this grows green or white corrosion, and the owner removes this corrosion and thinks all is well. I am not sure how it is NOT all OK, but I have witnessed on more than one occassion weird electrical issues stemo from battery cables which once had visible corrosion removed. opening up teh wirin insulation shows the corrosion wicked well up the wire stranding, and then sometimes the 6 or 4 sae gauge wire would refuse to pass any current, or cause weird intermittent issues that are easily solved with new battery cables.
Do be aware that many parts store cables, use steel ring terminals.
On a scale of 1 to 100 and copper being 100, steel is about a 4, depending on teh alloy, and steel rusts.
If you need new battery cables:https://www.genuinedealz.com/collections/custom-cables
The prices are likely less than parts store crap, and he uses professional tools and top quality components and stuff arrives quickly with free shipping.
Parts store cables are SAE gauge, which is 6 to 12% thinner than AWG, american wire gauge, with correspondingly less ampacity.