When it idles well, you have good acceleration from stop to WOT without any hesitation or bogging, you have visible smoke at WOT, and your temps are within the recommended range for your mill. You can have all that and still be running rich so then lean your HSN for performance. Basically leaning it 1/4 turn at a time until your temps get too high, then kick it back a 1/4 notch.
Do you want all 8? Just buy direct from Himoto via exportpro on the himoto website. The ally ones are more expensive (08041) are usd 18 for 2, making usd 72 plus usd 10 postage total of usd 82. I would estimate about £65 if you need 8 of them.
There are cheaper metal shocks (08058) at usd 10 per pair making a total of usd 50 including postage estimate around £40.
and hit spare part list under your model. This brings up all the parts for your truck and prices, and how to order. Payment has to be made via paypal so maybe your folks could do this for you if they have paypal account.