silverR50

Alright so Ive put about 6k miles on my new to me 97 SE manual. I live in a rural area where the speed limit rarely goes above 55-65 mph. a couple weeks ago i had to get on the interstate (75mph) and noticed my 5th gear and sometimes 4th gear is basically worthless at interstate speeds. I can push the pedal all the way to the ground and the rpms will drop going 65-70 mph. I can get the truck up to 75 on a slight downgrade and in 5th gear it will hold 75 at 2-3k rpm no problem. Its an older under powered truck so i thought nothing of it. HOWEVER this past weekend while doing some offroading above 10k feet I was going up a pass and started to smell fuel, it's an old car so again thought nothing of it. Got out at the top of the pass and saw fuel literally spewing out of my gas tank where the gas cap is and running down the side of my truck. Which makes me think im having an EVAP or some sort of fuel pressure issue. I replaced the fuel cap with an OEM nissan one. Took the truck up to a local spot above 10k with an incline and threw a p0440 code and it felt like a had almost no power trying to get up a loose section, it actually died on me in 4low with the pedal to the ground in 1st gear trying to start on an incline. had to back up and hit the incline with a little more speed and it made it up but if the incline was any longer the rpms would have dropped to the point of the truck dying. I cleared the code and put about 40 miles on the truck and the SES light hasnt come back... Ive searched all over and this seems to be a unique issue... Ive Ordered: Vapor canister purge solenoid Valve Vapor canister Vent solenoid I took the charcoal canister off and it seems to be fine, nothing rattles or anything and there are not bits of charcoal in any of my lines. Anyone have any thoughts?