Additive product

[jcgjaguar]

Hello, (in advance, sorry for bad english, i'm french)

I have a problem with my XJR 1992. Manual Gear.

When i stop the motor, it makes a noise, and it's like if the motor trembles a little more than usual. (in fact the motor trembles a little too when i am in slow motion position)
A friend of me say that it's a problem of bad combustion.
It's because the car is not used so often, and he say there is a lot of bad things in the tank, and in the injection system since 20 years.
He said me that the motor can stop one day, (and perhaps broke), if i don't make a complete cleaning and purging of the tank and all system.

But, waiting this time of compleete inspection, he said me to put 2 products in the tank :

1) The Motul Stabilizer
2) The Motul Fuel System Clean

Do you think i can reasonabily put these additives in my XJR TWR ?????

I just want another opinion, because this motor is not a common motor.

Any ideas about these products, can they damage my motor, or not ?

Best regards.