Another new guy introduction

New to EFI tuning, but not new to EFI. Boat mechanic for 25 years, built some for an Alaska fishery. Lots of fab work, lots of turning wrenches on inboards, sterndrives, and outboards.
Never messed with tuning EFI, only diagnose and repair to factory specs. Now I'm trying to learn the other side. Have 2 project trucks, both are square body Chevy crew cabs.
One is real project converting from 2wd to 4wd, Cummins swap with NV4500/205. the other one I'm trying to leave relatively stock. The Cummins truck was the only project, until this one popped up
and I couldn't pass up the opportunity for the price, so here's what I've got... 1989 Chevy 1 ton crew cab 4wd, 350 TBI/4 speed manual 6" lift and 37" tires. This is how I got it.
Been sitting under a spruce tree for who knows how long. Covered in moss, mushrooms, and ferns. Towed it home, wife pressure washed the moss off it.
Then could see it was forest service green under a crummy coat of white. The green wasn't even scuffed to apply the white, so I hand washed it with scotch bright pads to remove the rest of the
moss that wouldn't come off. Cleaned up under the hood to assess the engine condition. TBI and some of the serpentine belt parts were missing. Starter, alternator, and water pump were seized.
And the engine wiring harness had been creatively altered by someone at some point. During this time I had a 1989 Chevy suburban that was donating body parts to the other crew cab project and it had a good running 350.
So it only made sense to me to just cut my losses with the engine in the crummy as I wasn't sure how many years spruce needles and mouse poop had been going down the intake, and just swap in the engine
from the suburban. The only thing I didn't do was retain the factory engine oil cooler stuff. I also used the engine wiring harness from the suburban. Replace front and rear crankshaft seals, oil pan gasket, valve cover
gaskets, cap, rotor, spark plugs, wires, air filter, oil filter, oil, fuel filter. Before adding the new fuel filter I operated the fuel pump to flush fresh non ethanol gas through it, then flushed out the line to the TBI before installing the engine.
Combined exhaust parts from the crummy and suburban to make a relatively stock exhaust minus the cat which wasn't there on either rig. Started up, ran fine, took it for a drive. Been working through steering, suspension issues for drivability.
One day while driving it, it lost some power. I'm sure I could install an HEI distributor and a carburetor and my problem would be solved, but now I've started down this road of learning more about EFI but more specifically TBI injection.

Hi,

Welcome to the forum! Sounds like quite a project. Years ago I met a retired locomotive mechanic with a 453 Detroit in a Ford F350. I was a GM guy so I asked Why Ford? GM Frame just isn't the same class... Even the one ton needs help to handle this. I have not heard how the square body chassis holds up when Cummins powered so this might be interesting...

The TBI system was designed with coolant flowing through the manifold and a Thermac system on the air cleaner. All of this gives better combustion but decreases power. If you can block coolant flow through the manifold and get cool air into the engine you can gain power. It's even better if you can utilize intake air temp readings although that requires an ecm swap, sensor installation, and some code changes to be effective. Switching to a low end cam can make that thing pull really well with those tires but you'll need tuning to take advantage of it. One way or another, it sounds like you're going to have fun learning.