I am a fan of Seafoam. The way I understand, it is basically a mixture of very light oils. So it doesn't really harm anything, it just cleans.

It can be used in 3 ways. Added to the fuel tank, it cleans fuel lines and injectors. Added to the intake manifold while running, it may clean upper engine deposits. Added to the crankcase for a few miles before an oil change, it cleans the oil system. I think it is a good idea to use Seafoam occasionally, maybe every 10 or 20,000 km.

For a cheap upgrade, the old CPI fuel spider can be upgraded to the MPFI spider if it has not already been done. If you can find a used spider at an autowrecker, this upgrade is cheap, otherwise a new spider would be expensive. At the same time, you could clean deposits from the throttle body.

 

If you can find a nice MPFI unit, I agree it can be worth installing it. It is too bad they are so hard/impossible to find new any more. I replaced mine when I replaced/upgraded my lower intake manifold gaskets in about 2017. At the time I got a new AC Delco set from Rock Auto. I didn't realize I fortunate I was at the time.

This link has a quick description of the differences in types of injectors: https://www.motormanfuelinjection.co...onversion.html

 

I upgraded my spider with one from Standard Motor back in 2021. They're still working and my boy runs great. When I had them out when I was doing a top motor rebuild a month or so ago, the nozzles looked still new, no build up. A pricey upgrade but worth it.

 

I've used Seafoam a few times, but only on the fuel system. I've never added it to the crankcase.

I will share that my fuel gauge had recently started not changing on the lower half of the tank, staying at 1/2 full until you either ran out of fuel or it would suddenly go from 1/2 to E. I was just monitoring my range by the trip odometer, but it may have caused me to use my AAA subscription a time or two when I underestimated or forgot to reset the trip odometer after filling up.

I recently decided to run a can of Seafoam through my fuel just as part of my winter preparation so that hopefully the fuel system is ready for the cold Canadian weather, and dang if that didn't fix the fuel sending unit too! My fuel gauge is now working properly and doesn't get stuck at 1/2 full. I'm guessing that there was just some buildup on the contacts of the float that the Seafoam dissolved, allowing it to make contact again.

Anyways, I'm a fan of Seafoam!

 

The only reason I've heard of using seafoam in the crankcase is to cover up a knock while it rolls across an auction block. The problem I've been told is it cleans too much, you'll have new leaks after using it.

My Blazer is carbureted, but coming from the car side I'd have to recommend a throttle body controller for a cheap wake-up. Not sure what options you might have for a 2000 4.3.