Sounds like you are doing good! That was a good bit of progress for your first go at it. Many new nitro hobbyists have a few more hangups before even getting through the process.

Your description sounds 99.9% like it's too lean on the HSN. If the engine takes off great and then bogs it is too lean on the HSN. Basically, it starts starving for fuel and cuts out. You definitely don't want to get crazy with the needles; 1-2 turns is HUGE for a nitro engine. Most fine tuning is gonna be in 1/16-1/8 turns. You probably overshot the sweet spot.

No problem at all. Set both needles to factory settings. As a rule of thumb, you always want to tune the HSN first. So, start the truck and get it warmed up. You do not want to attempt a tune when the engine isn't warmed up fully. When it's warm, start making WOT straight line passes. Once you make a few passes, bring it in and turn the HSN in 1/8 turn (turns in /clockwise = lean, turns out / counter clockwise = rich). This is the HSN, so don't focus on faster take offs, focus on higher top speed. The truck should be a hair faster now. Make a few more passes, and repeat the process until the truck is winding up good and shifting into second gear; once you get close to the sweet spot, don't tune in more then 1/16 turn increments. Don't tune by temperature as your first guide. Once you get the truck shifting and clearing out the pipe good, you will probably find your temps around 230-250 which is just right for a big block stock engine. Good temperatures is a CAUSE of a well tuned engine, it shouldn't be the guide. You will find as you get better that you basically know what temp range your engine is just by how it is running.

Don't forget, this is all without even touching your LSN. Now, once the truck is shifting into 2nd gear and hauling butt at WOT, it's time to tune the LSN. Bring the truck in, and start turning the LSN, 1/8 turns at a time and repeat until you get strong takeoffs from a dead stop.

Once the LSN is dialed in, your truck should have great low and top end power and shift into 2nd.

Good luck!