Ya can tell a good rattle if you hold a screwdriver to ya rocker cover whilst running and listening to the other end , Sound like ya got some big issues with your lump

Fuel gauge

There a cunt to put it simple Ive had loads of xr,s with dodgey fuel gauges< as its had a different dash in id suggest it may be something to do with that.
But first off id buy beg borrow or cadge a good voltmeter, Set on ohms measure the resistance on the sender then again after say 10 or more miles, See if it goes down or not , Then check every connection from that sender upwards to your dial

Your smoke...

Take your hose off the turbo, Is there much play? Id assume if theres not aklot of play ur seal may be alreet but not to eliminate

Hows the oil? Does it seem like its never been changed?

Cvh engines are renowned for valve stem oil seals fucking up hence smoke, With your top end sounding like a shopping trolly id also think about taking it apart and replacing the cam , lifters , seals ect ect < whilst at it think about upgrades too as you have it apart...
But id focus on them points
There also a slag for breathing oil so pull the breather pipes off as said one by one and give them a good clean out, n blow not forgettin the crankcase oil breather which can get full of shit if its been run dirty and spanked for years on end



Trouble is with these engines is there spanktastic, Every fucker and there dog have spanked it and quite often dont bother changing oil and maintaining them setting up ect ect. Just up boost and spank. Then they end ep with a big pinking loadsa smoke and shopping trolly heads.