My Go Tech 7 port has lost almost its compression after 3 gallons and the lack of low end is noticeble.
I'm considering buying one of these engines. I am open for other suggestions. Pros&Cons?

Picco P7R EVO 2
Picco P7R EVO 3
OS MAX V-SPEC T
Ofna Jamin
Novarossi RX21P5XS 5 port
RB Concept S7 L2G
Ninja JX Buggy Engine .21 5 Port
O'Donnell Super Sport .21cu in (3.4cc) Off-Road Engine

Sorry about the long list, but I'm really uncertain about which engine to buy.
I want an reliable engine that lasts more than 3 gallons, with good fuel consumption. Any suggestions?
Thanks