Please help with 2010 te450. Cuts out when idling and backfires/pops

Hi guys. This is my first post to the forum. I'm a noob poster, bike rider and mechanic. I Bought my first bike a couple of months ago. I think I bought a good bike, the guy I bought it off seems to have looked after it really well.
Bought it with 3800ks on it. Now it has 4600ks.

I'm determent service and fix it myself as much as possible. It's been running fine until a few weeks ago.
It started backfiring a lot when dropping the throttle. It also cuts out when it's idling, hot and cold.

I have to mention that I changed the fuel tank back to the stock standard one, changed engine oil + cleaned filters and cleaned and re oiled the air filter ( saying this because I think the problems started occurring or at least got worse after this)
Since I changed the fuel tank over I started smelling a burnt plastic/electrical smell from the front of the bike.
Just when idling too, not just driving. I have had the bike running with the tank lifted off to try and locate the smell but without success.

I have driven it in wet conditions and dropped it in puddles a few times too.

I googled the shit out of it and asked anyone who knew more than I do.
I have done what I can:

So far I have:
Adjusted valves ( not sure it needed it but just
in case)
Cleaned out the fuel tank
Changed the fuel filter inside the tank
Cleaned the injector, there was some green wire casing looking material in there.
Cleaned the air filter again, there was a bit of engine oil in the box.
Checked all(I think) wiring for damage, rubbing or burn.

Handed it in to a local bike shop. They don't know what's wrong with it after $65 (not too bad for a funny story to tell) I told the mechanic everything I did to the bike before I handed it in. All he did was change the fuel filter again and check the injector again. The fuel filter they sold me and I put in there apparently doesn't like being submerged in fuel, so he put the same one in there.. I also asked if he thinks it might be the TPS but he doesn't know how to check it.. He did say he thinks it's running lean (his 5 cents?) hehe
They may or may not figure it out but when I'm paying them $100/hr and it might take them hours to figure it out... Eeeeeh. So I got the bike back in my garage..

I'm about to bypass the fuel filter and try to see if it runs better but I doubt it's that.


Any clue how to get my bike running like a dream again?

Make sure your header is tight to the exhaust/head before you spend any money on tuning.

...and check your manifold clamps & mounts. also look for a vacuum port that may be leaking. is your injector leaking air around it? Check the spark plug and cap.

it'll probably be related to something you did to the bike earlier.

find the source of the burning smell, too. (something on or near the header? or another part of the exhaust? electrical fault?)

Look for rubbed wires, go here and look at pics
https://www.google.com/search?q=rubbed wire site:cafehusky.com&espv=2&biw=1227&bih=835&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjXvqDuu4nOAhWE3YMKHYv5BkUQ_AUIBygC&dpr=1.1

Here are some pics of intake manifolds
https://www.google.com/search?q=intake manifold site:cafehusky.com&biw=1227&bih=835&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi-sILfvYnOAhUHbiYKHd5iA78Q_AUIBygC

Was the green stuff this color? If so, that's a specially shaped washer that is part of the injector, it gets torn when R&Ring the injector

Just rode with a friend who has a new EXC 500, was cutting out, popping, would get better then get worse, turns out it was the ground wire from the battery had broken and was just barely hanging on by a strand of wire. Got it fixed and the bike ran great

Here we were pulling the fuel pump because we thought it was a slipped hose or clogged filter, and the owner just wiggled the frame ground connection and it parted. On a fuel injected bike, electrics are very important.