So I have a customer who wants "100 more HP". I don't think he really knows what that means but he wants to get an upgraded turbo, injectors, fuel plate, cold air intake, and really quiet/more power exhaust. What are decent upgrades to recommend him without breaking the bank?

A #10 BD fuel plate, 4 or 5" exhaust and the cold air kit will probably give him 70 or so more HP and 150 lbs more torque.
Just make sure it's a BD plate...not some generic copy....those aren't very good.
You could also put some upgraded governor springs in the pump which will give him an honest 400 RPM more pulling range. Nice for towing.

The 12 valve engine is a fantastic motor.....mainly the 96-98.5 engine which has the better fuel pump. Cheapest upgrade is a fuel plate BUT it is really recommended to upgrade the exhaust also to a larger, non-restrictive system to let the heat out.

Once you start throwing more fuel to the motor, it will get hot quicker when you lay in to it and you really don't want to keep all that heat bottled up with a stock size system.

I have only done this to a truck with a manual transmission and it worked great!! I have an automatic 12 valve now that I am thinking about putting a plate on it but not sure how well the automatic will respond to this plate??

With the fuel plate and a lock up convertor, when the truck hits lockup, it'll just start pulling hard.

The power side of it can be done relatively cheap and simple. A good fuel plate, advance the pump timing, a good exhaust system, and a boost elbow in a stock turbo will get you a long ways from the truck he's used to.

One thing to make sure is that your customer is aware what supporting mods may have to be done and how the truck is going to behave with the extra power. An EGT gauge is a necessity once you start tweaking on a 12 valve. If it's an auto, it is going to need a good torque converter and valve body at a bare minimum. If you start getting too crazy then it will probably need gone through. If it's a stick then a stock clutch may be sufficient, but it may end up slipping and need a good aftermarket unit.

I already built his trans in anticipation of this with extra clutches, cooling and a shift kit. I have a billet low stall converter (300 rpm under stock with a stock engine)brand new on the shelf with his name on it. The truck has a Dana 80. When we did his head gasket we put in some $800 head studs. He still has the cat in it and he can ditch that if he wants.

He seems bent on upgradeing the turbo and he says the 24v turbo is better, is that a good idea?

Like I said.....70 or HP and 150 more torque. THAT won't kill the truck IF he drives it sensibly. I put at least that much into my first gen....never had a problem because I push it BUT I don't beat on it. Common sense going up hills tells you not to have the pedal to the floor....people with 5th wheels in excess of 10000 lbs are famous for holding the pedal down and not using the gears. No wonder the transmissions overheat and fail.
Put dozens of fuel plates in trucks and I can tell you that the only ones that had trouble were the very ones I just described. They shouldn't even have been towing...obviously...some people need to take a course...

First....GAUGES

3K or 4K gov spring kit (HD valve spring upgrade) + AFC tune + fuel plate mod + timing + 4inch exhaust.